diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000000..fbbbb71463
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,6 @@
+[submodule "vendor/traceur"]
+	path = vendor/traceur
+	url = https://github.com/google/traceur-compiler
+[submodule "vendor/regenerator"]
+	path = vendor/regenerator
+	url = https://github.com/facebook/regenerator
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b3e4254a3e..dfd5d7723b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,63 @@
 # Changelog
 
-Gaps between patch versions are faulty/broken releases.
+> **Tags:**
+> - [New Feature]
+> - [Bug Fix]
+> - [Spec Compliancy]
+> - [Breaking Change]
+> - [Documentation]
+> - [Internal]
+> - [Polish]
+
+_Note: Gaps between patch versions are faulty/broken releases._
+
+## 2.6.3
+
+ * **Bug Fix**
+  * Fix 2.6.0 regression caused by faulty export default from a source handling.
+
+## 2.6.2
+
+ * **Bug Fix**
+  * Fix rest parameter keys when on functions with params.
+
+## 2.6.1
+
+ * **Bug Fix**
+  * Fix rest parameter arguments key.
+
+## 2.6.0
+
+ * **Bug Fix**
+  * Better handling of number literal property keys.
+  * Handle `NewExpression` paren insertion edegcases better.
+ * **Internal**
+  * Fix incorrect AST node `identifier("this")`.
+  * Better `toIdentifier` method that handles reserved words.
+  * Upgrade `acorn-6to5`.
+    * Fix exponentiation operator precedence.
+    * Fix line terminators after async contextual keywords.
+    * Add semicolons as class elements inside of a class body.
+  * Upgrade to `core-js` 4.0.0.
+  * Upgrade to `regenerator` 0.8.3.
+    * Fix non-loop labeled statements.
+ * **New Feature**
+  * Basic destructuring defaults
+  * Add `.es` to list of supported extensions.
+  * Add optional `typeofSymbol` transformer.
+  * Use a `for` loop for rest parameters instead of `Array.prototype.slice`.
+ * **Polish**
+  * Move `"use strict";` to inside module bodies instead of at the top of the file.
+  * Better handling of dynamic imports.
+ * **Spec Compliancy**
+  * Class inheritance now has a `function` or `null` type check.
+  * Add `interopRequireWildcard` around wildcard imports and exports to handle non-object exports.
+
+## 2.5.0
+
+ * Remove `noDuplicateProperties` transformer.
+ * Better generated UIDs based on nodes.
+ * Default parameters now use `arguments[i]`, conditionals and variable declarations instead of using long-form if statements.
 
 ## 2.4.10
 
diff --git a/Makefile b/Makefile
index 797d3f41a6..b5101bbd91 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,23 @@ MOCHA_CMD = node_modules/mocha/bin/_mocha
 
 export NODE_ENV = test
 
-.PHONY: clean test test-cov test-clean lint test-travis test-spec test-browser publish bench build
+.PHONY: clean test test-cov test-clean lint test-travis test-spec test-browser publish bench build bootstrap
+
+build:
+	mkdir -p dist
+
+	node bin/cache-templates
+
+	node $(BROWSERIFY_CMD) -e lib/6to5/polyfill.js >dist/polyfill.js
+	node $(UGLIFY_CMD) dist/polyfill.js >dist/polyfill.min.js
+
+	node $(BROWSERIFY_CMD) lib/6to5/browser.js -s to5 >dist/6to5.js
+	node $(UGLIFY_CMD) dist/6to5.js >dist/6to5.min.js
+
+	node bin/6to5-runtime >dist/runtime.js
+	node $(UGLIFY_CMD) dist/runtime.js >dist/runtime.min.js
+
+	rm -rf templates.json
 
 clean:
 	rm -rf coverage templates.json test/tmp dist
@@ -45,22 +61,6 @@ test-browser:
 
 	test -n "`which open`" && open test/browser.html
 
-build:
-	mkdir -p dist
-
-	node bin/cache-templates
-
-	node $(BROWSERIFY_CMD) -e lib/6to5/polyfill.js >dist/polyfill.js
-	node $(UGLIFY_CMD) dist/polyfill.js >dist/polyfill.min.js
-
-	node $(BROWSERIFY_CMD) lib/6to5/browser.js -s to5 >dist/6to5.js
-	node $(UGLIFY_CMD) dist/6to5.js >dist/6to5.min.js
-
-	node bin/6to5-runtime >dist/runtime.js
-	node $(UGLIFY_CMD) dist/runtime.js >dist/runtime.min.js
-
-	rm -rf templates.json
-
 publish:
 	git pull --rebase
 
@@ -81,3 +81,8 @@ publish:
 	git push --follow-tags
 
 	rm -rf templates.json browser.js runtime.js browser-polyfill.js
+
+bootstrap:
+	npm install
+	git submodule update --init
+	cd vendor/regenerator; npm install
diff --git a/NOTES.md b/NOTES.md
new file mode 100644
index 0000000000..11962b3ca5
--- /dev/null
+++ b/NOTES.md
@@ -0,0 +1,8 @@
+# Notes
+
+ * Wildcard exports/imports wont normalise if `export default` is a non-object.
+
+## 3.0.0 breaking changes
+
+ * Remove `allowImportExportEverywhere` option from acorn.
+ * Remove this shorthand from playground.
diff --git a/doc/browser.md b/doc/browser.md
deleted file mode 100644
index 408ddd77d0..0000000000
--- a/doc/browser.md
+++ /dev/null
@@ -1,65 +0,0 @@
-# Browser
-
-A browser version of 6to5 is available from `browser.js` inside the 6to5
-directory in an npm release.
-
-## Scripts
-
-While it's not recommended for serious use, when the browser version is included
-all scripts with the type `text/ecmascript-6` and `text/6to5` are automatically
-compiled and ran.
-
-For example:
-
-```html
-<script src="node_modules/6to5/browser.js"></script>
-<script type="text/6to5">
-class Test {
-  test() {
-    return "test";
-  }
-}
-
-var test = new Test;
-test.test();
-</script>
-```
-
-## Build
-
-You can build a browser version of the compiler by running the following in the
-6to5 directory:
-
-```sh
-$ make build
-```
-
-This will output the files `dist/6to5.js` and `dist/6to5.min.js`.
-
-## Test
-
-To test 6to5 in your browser run:
-
-```sh
-$ make test-browser
-```
-
-And open `test/browser.html` in your browser if it doesn't open automatically.
-
-## API
-
-### to5.transform(code, [opts])
-
-See [options](usage.md#options) for additional documentation.
-
-```javascript
-to5.transform("class Test {}").code;
-```
-
-### to5.run(code, [opts])
-
-See [options](usage.md#options) for additional documentation.
-
-```javascript
-to5.run("class Test {}");
-```
diff --git a/doc/caveats.md b/doc/caveats.md
deleted file mode 100644
index 4e953bd9d1..0000000000
--- a/doc/caveats.md
+++ /dev/null
@@ -1,62 +0,0 @@
-# Caveats
-
-In order for certain features to work they require certain polyfills. You can
-satisfy **all** 6to5 feature requirements by using the included
-[polyfill](polyfill.md).
-
-You may alternatively selectively include what you need:
-
-| Feature                     | Requirements                                                                                                           |
-| --------------------------- | ---------------------------------------------------------------------------------------------------------------------- |
-| Abstract References         | [experimental](experimental.md), `Symbol`                                                                              |
-| Array destructuring         | `Array.from`                                                                                                           |
-| Async functions, Generators | [experimental](experimental.md), [regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) |
-| Comprehensions              | [experimental](experimental.md), `Array.from`                                                                          |
-| For Of                      | `Symbol`, `prototype[Symbol.iterator]`                                                                                 |
-| Modules                     | `Object.assign`*                                                                                                       |
-| Object spread/rest          | [experimental](experimental.md), `Object.assign`                                                                       |
-| Spread                      | `Array.from`                                                                                                           |
-
-*Only required for exporting a non-function `default` with additional `export`s.
-
-## ES5
-
-Since 6to5 assumes that your code will be ran in an ES5 environment it uses ES5
-functions. So if you're using an environment that has limited or no support for
-ES5 such as lower versions of IE then using the
-[es5-shim](https://github.com/es-shims/es5-shim) along with the
-[6to5 polyfill](polyfill.md) will add support for these methods.
-
-## Internet Explorer
-
-### Classes (10 and below)
-
-If you're inheriting from a class then static properties are inherited from it
-via [\_\_proto\_\_](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto),
-this is widely supported but you may run into problems with much older browsers.
-
-**NOTE:** `__proto__` is not supported in IE <= 10 so static properties
-**will not** be inherited. A possible workaround is to use `super();`:
-
-```javascript
-class Foo {
-  static foo() {
-
-  }
-}
-
-class Bar extends Foo {
-  static foo() {
-    super();
-  }
-}
-```
-
-## Getters/setters (8 and below)
-
-In IE8 `Object.defineProperty` can only be used on DOM objects. This is
-unfortunate as it's required to set getters and setters. Due to this if
-you plan on supporting IE8 or below then the user of getters and setters
-isn't recommended.
-
-**Reference**: [MDN](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty#Internet_Explorer_8_specific_notes).
diff --git a/doc/differences.md b/doc/differences.md
deleted file mode 100644
index ff27c62378..0000000000
--- a/doc/differences.md
+++ /dev/null
@@ -1,137 +0,0 @@
-# Differences
-
-There are three main points that separate 6to5 from all other transpilers.
-
-### Readable code
-
-The fundamental concept behind 6to5 is that the generated code must be close as
-possible to the original, retaining all the same formatting and readability.
-
-Many other transpilers are just concerned with making the code work while 6to5
-is concerned with making sure it works **and** is readable at the same time.
-
-For example, given the following array comprehension:
-
-```javascript
-var seattlers = [for (c of customers) if (c.city == "Seattle") { name: c.name, age: c.age }];
-```
-
-is generated to the following with 6to5:
-
-```javascript
-var seattlers = Array.from(customers).filter(function (c) {
-  return c.city == "Seattle";
-}).map(function (c) {
-  return {
-    name: c.name,
-    age: c.age
-  };
-});
-```
-
-The following is what Traceur generates:
-
-```javascript
-var seattlers = (function() {
-  var c;
-  var $__20 = 0,
-      $__21 = [];
-  for (var $__22 = customers[$traceurRuntime.toProperty(Symbol.iterator)](),
-      $__23; !($__23 = $__22.next()).done; ) {
-    c = $__23.value;
-    if (c.city == "Seattle")
-      $traceurRuntime.setProperty($__21, $__20++, {
-        name: c.name,
-        age: c.age
-      });
-  }
-  return $__21;
-}());
-```
-
-As you can tell, it's not very pretty. Instead of mapping directly to a
-runtime, like other transpilers, 6to5 maps directly to the equivalent ES5.
-
-Sometimes there are little inline functions that 6to5 needs. These are
-placed at the top of your file much like coffee-script does. If these
-bother you then you can use the [optional runtime](optional-runtime.md).
-We promise that these inline functions will never be significant and will
-always be used as little as possible.
-
-### Static analysis
-
-6to5 uses a lot of static analysis to simplify code as much as possible.
-Not many other transpilers do this, and those that do don't do it nearly
-as much as 6to5. This process is pretty intensive but it leads to higher
-quality code.
-
-### Spec compliancy
-
-6to5 prides itself on
-[spec compliancy](https://kangax.github.io/compat-table/es6/). We have
-excellent support for edgecases, something that many other transpilers
-suffer from, including Traceur. When you use 6to5 you can be confident
-that when you turn it off and use your code in a full ES6 environment
-**it'll just work**.
-
-## Comparison to other transpilers
-
-### Features
-
-|                              | 6to5 | Traceur | es6-transpiler | esnext | es6now | jstransform |
-| ---------------------------- | ---- | ------- | -------------- | ------ | ------ | ----------- |
-| Source maps                  | ✓    | ✓       | ✓              | ✓      |        | ✓           |
-| No compiler global pollution | ✓    |         | ✓              | ✓      |        | ✓           |
-| Optional runtime             | ✓    |         | ✓              |        |        | ✓           |
-| Browser compiler             | ✓    | ✓       |                | ✓      |        |             |
-
-### Language Support
-
-|                              | 6to5 | Traceur | es6-transpiler | esnext | es6now | jstransform |
-| ---------------------------- | ---- | ------- | -------------- | ------ | ------ | ----------- |
-| Abstract references          | ✓    |         |                |        |        |             |
-| Array comprehension          | ✓    | ✓       | ✓              |        |        |             |
-| Arrow functions              | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Async functions              | ✓    | ✓       |                | ✓      |        |             |
-| Async generator functions    | ✓    | ✓       |                |        |        |             |
-| Classes                      | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Computed property names      | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Constants                    | ✓    | ✓       | ✓              |        |        |             |
-| Default parameters           | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Destructuring                | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Exponentiation operator      | ✓    | ✓       |                |        |        |             |
-| Flow types                   | ✓    |         |                |        |        | ✓           |
-| For-of                       | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Generators                   | ✓    | ✓       |                | ✓      |        |             |
-| Generator comprehension      | ✓    | ✓       |                |        |        |             |
-| JSX                          | ✓    |         |                |        |        |             |
-| Let scoping                  | ✓    | ✓       | ✓              |        |        |             |
-| Modules                      | ✓    | ✓       |                |        | ✓      |             |
-| Object rest/spread           | ✓    |         |                |        |        | ✓           |
-| Property method assignment   | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Property name shorthand      | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Rest parameters              | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| React                        | ✓    |         |                |        |        |             |
-| Spread                       | ✓    | ✓       | ✓              | ✓      | ✓      |             |
-| Template literals            | ✓    | ✓       | ✓              | ✓      | ✓      | ✓           |
-| Unicode regex                | ✓    | ✓       | ✓              |        |        |             |
-
-### [Traceur](https://github.com/google/traceur-compiler)
-
-Traceur requires quite a bulky runtime (~75KB) and produces quite verbose code.
-While this can be trimmed down by selectively building the runtime, it's an
-unnecessary step when a large runtime can be eliminated entirely.
-
-### [es6now](https://github.com/zenparsing/es6now)
-
-es6now doesn't output sourcemaps. This is cited as a positive as line-to-line
-mapping is the goal. This however obviously doesn't retain column mapping
-resulting in the output code not being very pleasant.
-
-### [es6-transpiler](https://github.com/termi/es6-transpiler)
-
-The es6-transpiler compiler requires shims to operate which pollutes the global
-scope resulting in possible collisions.
-
-es6-transpiler maps line-by-line, just like es6now, this results in the same
-issues such as lack of column information and unpleasant code output.
diff --git a/doc/experimental.md b/doc/experimental.md
deleted file mode 100644
index 3546d0cb82..0000000000
--- a/doc/experimental.md
+++ /dev/null
@@ -1,8 +0,0 @@
-## Experimental
-
-6to5 also has experimental support for ES7 proposals. You can enable this with
-the `experimental: true` option when using the [Node API](#node) or
-`--experimental` when using the [CLI](#cli).
-
-**WARNING:** These proposals are subject to change so use with
-**extreme caution**.
diff --git a/doc/features.md b/doc/features.md
deleted file mode 100644
index a5c55fda81..0000000000
--- a/doc/features.md
+++ /dev/null
@@ -1,283 +0,0 @@
-# Features
-
-## Abstract references ([experimental](experimental.md)) ([spec](https://github.com/zenparsing/es-abstract-refs))
-
-```javascript
-foo::bar;
-foo::bar = baz;
-delete foo::bar;
-```
-
-## Array comprehensions ([experimental](experimental.md))
-
-```javascript
-var results = [for (c of customers) if (c.city == "Seattle") { name: c.name, age: c.age }]
-```
-
-## Arrow functions
-
-```javascript
-// Expression bodies
-var odds = evens.map(v => v + 1);
-var nums = evens.map((v, i) => v + i);
-
-// Statement bodies
-nums.forEach(v => {
-  if (v % 5 === 0)
-    fives.push(v);
-});
-
-// Lexical this
-var bob = {
-  _name: "Bob",
-  _friends: [],
-  printFriends() {
-    this._friends.forEach(f => {
-      console.log(this._name + " knows " + f);
-    });
-  }
-};
-```
-
-## Async functions ([experimental](experimental.md)) ([spec](https://github.com/lukehoban/ecmascript-asyncawait))
-
-```javascript
-async function chainAnimationsAsync(elem, animations) {
-  for (var anim of animations) {
-    await anim(elem);
-  }
-}
-```
-
-## Async generator functions ([experimental](experimental.md)) ([spec](https://github.com/jhusain/asyncgenerator))
-
-```javascript
-
-```
-
-## Classes
-
-```javascript
-class SkinnedMesh extends THREE.Mesh {
-  constructor(geometry, materials) {
-    super(geometry, materials);
-
-    this.idMatrix = SkinnedMesh.defaultMatrix();
-    this.bones = [];
-    this.boneMatrices = [];
-    //...
-  }
-
-  update(camera) {
-    //...
-    super.update();
-  }
-
-  static defaultMatrix() {
-    return new THREE.Matrix4();
-  }
-}
-```
-
-## Computed property names
-
-```javascript
-var foo = "foo";
-var bar = "bar";
-var obj = {
-  ["foo" + bar]: "heh",
-  ["bar" + foo]: "noo",
-  foo: "foo",
-  bar: "bar"
-};
-```
-
-## Constants
-
-```javascript
-const MULTIPLIER = 5;
-console.log(2 * MULTIPLIER);
-
-MULTIPLIER = 6; // error
-var MULTIPLIER; // error
-```
-
-## Default parameters
-
-```javascript
-function f(x, y = 12) {
-  // y is 12 if not passed (or passed as undefined)
-  return x + y;
-}
-f(3) == 15
-```
-
-## Destructuring
-
-```javascript
-// list matching
-var [a, , b] = [1,2,3];
-
-// object matching
-var { op: a, lhs: { op: b }, rhs: c } = getASTNode();
-
-// object matching shorthand
-// binds `op`, `lhs` and `rhs` in scope
-var { op, lhs, rhs } = getASTNode();
-
-// Can be used in parameter position
-function g({ name: x }) {
-  console.log(x);
-}
-g({ name: 5 });
-
-// Fail-soft destructuring
-var [a] = [];
-a === undefined;
-```
-
-## Exponentiation operator ([experimental](experimental.md)) ([spec](https://github.com/rwaldron/exponentiation-operator))
-
-```javascript
-var a = 2;
-a **= 2;
-
-var squared = 2 ** 2;
-```
-
-## For-of
-
-```javascript
-for (var i of [1, 2, 3]) {
-  console.log(i * i);
-}
-```
-
-## Generators
-
-```javascript
-function* fibonacci() {
-  var pre = 0, cur = 1;
-  for (;;) {
-    var temp = pre;
-    pre = cur;
-    cur += temp;
-    yield cur;
-  }
-}
-
-for (var n of fibonacci()) {
-  // truncate the sequence at 1000
-  if (n > 1000) break;
-  console.log(n);
-}
-```
-
-## Generator comprehensions ([experimental](experimental.md))
-
-```javascript
-var nums = [1, 2, 3, 4, 5, 6];
-var multiples = (for (i of nums) if (i % 2) i * i);
-assert.equal(multiples.next().value, 1);
-assert.equal(multiples.next().value, 9);
-assert.equal(multiples.next().value, 25);
-```
-
-## Let scoping
-
-```javascript
-for (let i in arr) {
-  let v = arr[i];
-}
-```
-
-## Modules
-
-```javascript
-import "foo";
-import foo from "foo";
-import * as foo from "foo";
-import {bar} from "foo";
-import {foo as bar} from "foo";
-
-export { test };
-export var test = 5;
-export function test() {}
-
-export default test;
-```
-
-## Numeric literals
-
-```javascript
-0b111110111 === 503; // true
-0o767 === 503; // true
-```
-
-## Object spread/rest ([experimental](experimental.md)) ([spec](https://github.com/sebmarkbage/ecmascript-rest-spread))
-
-```javascript
-var n = { x, y, ...z };
-var { x, y, ...z } = { x: 1, y: 2, a: 3, b: 4 };
-```
-
-## Property method assignment
-
-```javascript
-var obj = {
-  foo() {
-    return "foobar";
-  },
-
-  get bar() {
-    return this._bar;
-  },
-
-  set bar(val) {
-    this._bar = val;
-  }
-};
-```
-
-## Property name shorthand
-
-```javascript
-function f(x, y) {
-  return { x, y };
-}
-```
-
-## Rest parameters
-
-```javascript
-function f(x, ...y) {
-  // y is an Array
-  return x * y.length;
-}
-f(3, "hello", true) == 6
-```
-
-## Spread
-
-```javascript
-function f(x, y, z) {
-  return x + y + z;
-}
-// Pass each elem of array as argument
-f(...[1,2,3]) == 6
-```
-
-## Template literals
-
-```javascript
-var x = 5;
-var y = 10;
-console.log(`${x} + ${y} = ${x + y}`); // "5 + 10 = 15"
-```
-## Unicode regex
-
-```javascript
-var string = 'foo💩bar';
-var match = string.match(/foo(.)bar/u);
-console.log(match[1]);
-```
diff --git a/doc/index.md b/doc/index.md
index d37e7d8eaf..160f97e74d 100644
--- a/doc/index.md
+++ b/doc/index.md
@@ -1,62 +1 @@
-**6to5** turns ES6+ code into vanilla ES5, so you can use next generation features **today.**
-
- - **Readable** - formatting is retained if possible so your generated code is as similar as possible.
- - **Extensible** - with a large range of [plugins](plugins.md) and **browser support**.
- - **Lossless** - **source map support** so you can debug your compiled code with ease.
- - **Compact** - maps directly to the equivalent ES5 with **no runtime**[\*](caveats.md).
-
-## Installation
-
-It's as easy as:
-
-    $ npm install -g 6to5
-
-## Usage
-
-Once you've installed 6to5, there are multiple paths you can take depending on
-how you want to use it.
-
-6to5 will simply compile your ES6+ script to ES5 if you pass it as an argument
-to the command-line tool `6to5`:
-
-```sh
-$ 6to5 script.js
-```
-
-If you have a file written using ES6+ and you just want to run it, `6to5-node`
-has you covered:
-
-```sh
-$ 6to5-node script.js
-```
-
-And it doesn't end here! To see all the ways you can use 6to5, check out the
-[Usage](http://6to5.github.io/usage.html) page.
-
-## [Features](features.md)
-
- - [Abstract references](features.md#abstract-references) ([experimental](experimental.md))
- - [Array comprehension](features.md#array-comprehension) ([experimental](experimental.md))
- - [Async functions](features.md#async-functions) ([experimental](experimental.md))
- - [Async generator functions](features.md#async-generator-functions) ([experimental](experimental.md))
- - [Arrow functions](features.md#arrow-functions)
- - [Classes](features.md#classes)
- - [Computed property names](features.md#computed-property-names)
- - [Constants](features.md#constants)
- - [Default parameters](features.md#default-parameters)
- - [Destructuring](features.md#destructuring)
- - [Exponentiation operator](features.md#exponentiation-operator) ([experimental](experimental.md))
- - [For-of](features.md#for-of)
- - [Generators](features.md#generators)
- - [Generator comprehension](features.md#generator-comprehension) ([experimental](experimental.md))
- - [Let scoping](features.md#let-scoping)
- - [Modules](features.md#modules)
- - [Numeric literals](features.md#numeric-literals)
- - [Object rest/spread](features.md#object-rest-spread) ([experimental](experimental.md))
- - [Property method assignment](features.md#property-method-assignment)
- - [Property name shorthand](features.md#property-name-shorthand)
- - [React/JSX](react.md)
- - [Rest parameters](features.md#rest-parameters)
- - [Spread](features.md#spread)
- - [Template literals](features.md#template-literals)
- - [Unicode regex](features.md#unicode-regex)
+See [6to5.github.io/docs](https://github.com/6to5/6to5.github.io/tree/master/docs).
diff --git a/doc/modules.md b/doc/modules.md
deleted file mode 100644
index f58c68416f..0000000000
--- a/doc/modules.md
+++ /dev/null
@@ -1,257 +0,0 @@
-# Modules
-
-## Usage
-
-### CLI
-
-```sh
-$ 6to5 --modules common script.js
-```
-
-### Node
-
-```javascript
-var to5 = require("6to5");
-to5.transform('import "foo";', { modules: "common" });
-```
-
-## Formats
-
- * [AMD](#amd)
- * [Common (Default)](#common-default)
- * [Ignore](#ignore)
- * [System](#system)
- * [UMD](#umd)
-
-### Common
-
-```sh
-$ 6to5 --modules common
-```
-
-**In**
-
-```javascript
-export default test;
-
-export {test};
-export var test = 5;
-
-import "foo";
-
-import foo from "foo";
-import * as foo from "foo";
-
-import {bar} from "foo";
-import {foo as bar} from "foo";
-```
-
-**Out**
-
-```javascript
-"use strict";
-
-var _interopRequire = function (obj) {
-  return obj && (obj["default"] || obj);
-};
-
-exports = module.exports = test;
-
-exports.test = test;
-var test = exports.test = 5;
-
-require("foo");
-
-var foo = _interopRequire(require("foo"));
-
-var foo = require("foo");
-
-var bar = require("foo").bar;
-var bar = require("foo").foo;
-```
-
-### AMD
-
-```sh
-$ 6to5 --modules amd
-```
-
-**In**
-
-```javascript
-import foo from "foo";
-
-export function bar() {
-  return foo("foobar");
-}
-```
-
-**Out**
-
-```javascript
-define(["exports", "foo"], function (exports, _foo) {
-  "use strict";
-
-  var _interopRequire = function (obj) {
-    return obj && (obj["default"] || obj);
-  };
-
-  exports.bar = bar;
-  var foo = _interopRequire(_foo);
-
-  function bar() {
-    return foo("foobar");
-  }
-});
-```
-
-You can optionally specify to include the module id (using the `--amd-module-id` argument):
-
-```javascript
-define("filename", ["exports", "foo"], function (exports, _foo) {})
-```
-
-### UMD
-
-```sh
-$ 6to5 --modules umd
-```
-
-**In**
-
-```javascript
-import foo from "foo";
-
-export function bar() {
-  return foo("foobar");
-}
-```
-
-**Out**
-
-```javascript
-(function (factory) {
-  if (typeof define === "function" && define.amd) {
-    define(["exports", "foo"], factory);
-  } else if (typeof exports !== "undefined") {
-    factory(exports, require("foo"));
-  }
-})(function (exports, _foo) {
-  "use strict";
-
-  var _interopRequire = function (obj) {
-    return obj && (obj["default"] || obj);
-  };
-
-  exports.bar = bar;
-  var foo = _interopRequire(_foo);
-
-  function bar() {
-    return foo("foobar");
-  }
-});
-```
-
-### Ignore
-
-```sh
-$ 6to5 --modules ignore
-```
-
-**In**
-
-```javascript
-import foo from "foo";
-
-export function bar() {
-  return foo("foobar");
-}
-```
-
-**Out**
-
-```javascript
-function bar() {
-  return foo("foobar");
-}
-```
-
-### System
-
-```sh
-$ 6to5 --modules system
-```
-
-**In**
-
-```javascript
-import foo from "foo";
-
-export function bar() {
-  return foo("foobar");
-}
-```
-
-**Out**
-
-```javascript
-System.register("bar", ["foo"], function (_export) {
-  "use strict";
-
-  var __moduleName = "bar";
-
-  var foo;
-  function bar() {
-    return foo("foobar");
-  }
-  return {
-    setters: [function (m) {
-      foo = m.default;
-    }],
-    execute: function () {
-      _export("bar", bar);
-    }
-  };
-});
-```
-
-## Custom
-
-You can alternatively specify module names instead of one of the built-in types.
-
-```sh
-$ 6to5 --modules custom-module-formatter
-```
-
-**node_modules/custom-module-formatter/index.js**
-
-```javascript
-module.exports = ModuleFormatter;
-
-function ModuleFormatter() {
-
-}
-
-ModuleFormatter.prototype.transform = function (ast) {
-  // this is ran after all transformers have had their turn at modifying the ast
-  // feel free to modify this however
-};
-
-ModuleFormatter.prototype.importDeclaration = function (node, nodes) {
-  // node is an ImportDeclaration
-};
-
-ModuleFormatter.prototype.importSpecifier = function (specifier, node, nodes) {
-  // specifier is an ImportSpecifier
-  // node is an ImportDeclaration
-};
-
-ModuleFormatter.prototype.exportDeclaration = function (node, nodes) {
-  // node is an ExportDeclaration
-};
-
-ModuleFormatter.prototype.exportSpecifier = function (specifier, node, nodes) {
-  // specifier is an ExportSpecifier
-  // node is an ExportDeclaration
-};
-```
diff --git a/doc/optional-runtime.md b/doc/optional-runtime.md
deleted file mode 100644
index ee00e657b9..0000000000
--- a/doc/optional-runtime.md
+++ /dev/null
@@ -1,57 +0,0 @@
-# Optional runtime
-
-6to5 has a few helper functions that'll be placed at the top of the generated
-code if needed so it's not inlined multiple times throughout that file. This may
-become an issue if you have multiple files, especially when you're sending them
-to the browser. gzip alleviates most of this concern but it's still not ideal.
-
-You can tell 6to5 to not place any declarations at the top of your files and
-instead just point them to a reference contained within the runtime.
-
-Simply use the following option if you're using the [Node API](usage.md#node):
-
-```javascript
-{
-  runtime: true
-}
-```
-
-or the following flag if you're using the [CLI](usage.md#cli):
-
-```ssh
-$ 6to5 --runtime
-```
-
-Then just include the runtime before your generated code.
-
-## Getting the runtime
-
-You can get the runtime via either:
-
-```sh
-$ 6to5-runtime
-```
-
-or
-
-```javascript
-require("6to5").runtime();
-```
-
-or from an npm release in `runtime.js` from the 6to5 directory.
-
-## Customising namespace
-
-You can also customise the runtime namespace by passing an optional namespace
-argument:
-
-```javascript
-require("6to5").runtime("myCustomNamespace");
-```
-
-```sh
-$ 6to5-runtime myCustomNamespace
-```
-
-See [Options - runtime](usage.md#options) for documentation on changing the
-reference in generated code.
diff --git a/doc/playground.md b/doc/playground.md
deleted file mode 100644
index 985bc5409d..0000000000
--- a/doc/playground.md
+++ /dev/null
@@ -1,140 +0,0 @@
-# Playground
-
-Playground is a proving ground for **possible** ES7 proposals.
-
-**NOTE: These features are in no way endorsed by Ecma International and are not a part of ES6. They might become a part of ECMAScript in the future.**
-
-## Usage
-
-    $ 6to5 --playground
-
-```javascript
-to5.transform("code", { playground: true });
-```
-
-**NOTE:** Enabling `playground` also enables [experimental support](experimental.md).
-
-## Features
-
- * [Memoization operator](#memoization-operator)
- * [Method binding](#method-binding)
- * [Method binding function shorthand](#method-binding-function-shorthand)
- * [Object getter memoization](#object-getter-memoization)
- * [This shorthand](#this-shorthand)
-
-### Memoization assignment operator
-
-The memoization assignment operator allows you to lazily set an object property.
-It checks whether there's a property defined on the object and if there isn't then
-the right hand value is set.
-
-This means that `obj.x` in the following `var x = { x: undefined }; obj.x ?= 2;`
-will still be `undefined` because it's already been defined on the object.
-
-```javascript
-var obj = {};
-obj.x ?= 2;
-obj.x; // 2
-
-obj = { x: 1 };
-obj.x ?= 2;
-obj.x; // 1
-
-obj = { x: undefined }
-obj.x ?= 2;
-obj.x; // undefined
-```
-
-```javascript
-var obj = {};
-obj.x ?= 2;
-```
-
-equivalent to
-
-```javascript
-var obj = {};
-if (!Object.prototype.hasOwnProperty.call(obj, "x")) obj.x = 2;
-```
-
-### Method binding
-
-```javascript
-var fn = obj#method;
-var fn = obj#method("foob");
-```
-
-equivalent to
-
-```javascript
-var fn = obj.method.bind(obj);
-var fn = obj.method.bind(obj, "foob");
-```
-
-### Method binding function shorthand
-
-```javascript
-["foo", "bar"].map(#toUpperCase); // ["FOO", "BAR"]
-[1.1234, 23.53245, 3].map(#toFixed(2)); // ["1.12", "23.53", "3.00"]
-```
-
-equivalent to
-
-```javascript
-["foo", "bar"].map(function (val) { return val.toUpperCase(); });
-[1.1234, 23.53245, 3].map(function (val) { return val.toFixed(2); });
-```
-
-### Object getter memoization
-
-```javascript
-var foo = {
-  memo bar() {
-    return complex();
-  }
-};
-
-class Foo {
-  memo bar() {
-    return complex();
-  }
-}
-```
-
-equivalent to
-
-```javascript
-var foo = {
-  get bar() {
-    return Object.defineProperty(this, "bar", {
-      value: complex(),
-      enumerable: true,
-      configurable: true,
-      writable: true
-    }).bar;
-  }
-};
-
-class Foo {
-  get bar() {
-    return Object.defineProperty(this, "bar", {
-      value: complex(),
-      enumerable: true,
-      configurable: true,
-      writable: true
-    }).bar;
-  }
-}
-```
-
-### This shorthand
-
-```javascript
-@foo
-```
-
-equivalent to
-
-```javascirpt
-this.foo
-```
diff --git a/doc/plugins.md b/doc/plugins.md
deleted file mode 100644
index 3785d31575..0000000000
--- a/doc/plugins.md
+++ /dev/null
@@ -1,33 +0,0 @@
-# Plugins
-
-## Build systems
-
- - [Broccoli](https://github.com/6to5/broccoli-6to5-transpiler)
- - [Browserify](https://github.com/6to5/6to5ify)
- - [Brunch](https://github.com/6to5/6to5-brunch)
- - [Duo](https://github.com/6to5/duo6to5)
- - [Gobble](https://github.com/6to5/gobble-6to5)
- - [Gulp](https://github.com/6to5/gulp-6to5)
- - [Grunt](https://github.com/6to5/grunt-6to5)
- - [Sprockets](https://github.com/josh/sprockets-es6) or via [Browserify](https://github.com/6to5/6to5-rails)
- - [webpack](https://github.com/6to5/6to5-loader)
-
-## Integrations
-
- - [Isparta](https://github.com/douglasduteil/isparta) - Code coverage with `karma` and `instanbul` using 6to5
- - [JSXHint](https://github.com/STRML/JSXHint) - A wrapper around JSHint to allow linting of JSX files
-
-## Bridges
-
- - [Ruby](https://github.com/6to5/6to5-ruby)
-
-## Testing
-
- - [Jest](https://github.com/6to5/6to5-jest)
- - [Karma](https://github.com/6to5/karma-6to5-preprocessor)
- - [Mocha](https://github.com/6to5/6to5-mocha)
-
-## Misc
-
- - [Connect](https://github.com/6to5/6to5-connect)
- - [Jade](https://github.com/6to5/jade-6to5)
diff --git a/doc/polyfill.md b/doc/polyfill.md
deleted file mode 100644
index a97e334fb7..0000000000
--- a/doc/polyfill.md
+++ /dev/null
@@ -1,34 +0,0 @@
-# Polyfill
-
-6to5 includes a polyfill that includes a custom
-[regenerator runtime](https://github.com/facebook/regenerator/blob/master/runtime.js) and
-[core.js](https://github.com/zloirock/core-js).
-
-This will emulate a full ES6 environment. This polyfill is automatically loaded
-when using [6to5-node](usage.md#node) and [6to5/register](usage.md#register-hook).
-
-## Usage
-
-### Node/Browserify
-
-You need to include the polyfill require at the top the **entry point** to your
-application.
-
-```javascript
-require("6to5/polyfill");
-```
-
-Fortunately, this is automatically loaded when using:
-
-```javascript
-require("6to5/register");
-```
-
-### Browser
-
-Available from the `browser-polyfill.js` file within the 6to5 directory of an
-npm release. This needs to be included **before** all your compiled 6to5 code.
-You can either prepend it to your compiled code or include it in a `<script>`
-before it.
-
-**NOTE:** Do not `require` this via browserify etc, use `6to5/polyfill`.
diff --git a/doc/react.md b/doc/react.md
deleted file mode 100644
index d73cc12247..0000000000
--- a/doc/react.md
+++ /dev/null
@@ -1,17 +0,0 @@
-# React/JSX
-
-6to5 has built-in support for React v0.12. Tags are automatically transformed to
-their equivalent `React.createElement(...)` and `displayName` is automatically
-inferred and added to all `React.createClass` calls.
-
-## Blacklist
-
-To disable this behaviour add `react` to your blacklist:
-
-```javascript
-to5.transform("code", { blacklist: ["react"] });
-```
-
-```sh
-$ 6to5 --blacklist react
-```
diff --git a/doc/usage.md b/doc/usage.md
deleted file mode 100644
index 84917bc0b0..0000000000
--- a/doc/usage.md
+++ /dev/null
@@ -1,259 +0,0 @@
-# Usage
-
-## CLI
-
-Compile the file `script.js` and output it to stdout.
-
-```sh
-$ 6to5 script.js
-```
-
-Compile the file `script.js` and output it to `script-compiled.js`.
-
-```sh
-$ 6to5 script.js --out-file script-compiled.js
-```
-
-Compile the file `script.js` and output it to `script-compiled.js` and save a
-source map to `script-compiled.js.map`.
-
-```sh
-$ 6to5 script.js --source-maps --out-file script-compiled.js
-```
-
-Compile the file `script.js` and output it to `script-compiled.js` with a source
-map embedded in a comment at the bottom.
-
-```sh
-$ 6to5 script.js --source-maps-inline --out-file script-compiled.js
-```
-
-Compile the entire `src` directory and output it to the `lib` directory.
-
-```sh
-$ 6to5 src --out-dir lib
-```
-
-Compile the entire `src` directory and output it to the one concatenated file.
-
-```sh
-$ 6to5 src --out-file script-compiled.js
-```
-
-Pipe a file in via stdin and output it to `script-compiled.js`
-
-```sh
-$ 6to5 --out-file script-compiled.js < script.js
-```
-
-### Node
-
-Launch a repl.
-
-```sh
-$ 6to5-node
-```
-
-Evaluate code.
-
-```sh
-$ 6to5-node -e "class Test { }"
-```
-
-Compile and run `test.js`.
-
-```sh
-$ 6to5-node test
-```
-
-## Node
-
-```javascript
-var to5 = require("6to5");
-```
-
-### to5.transform(code, [opts]);
-
-```javascript
-var result = to5.transform("code();", options);
-result.code;
-result.map;
-result.ast;
-```
-
-### to5.transformFileSync(filename, [opts])
-
-```javascript
-to5.transformFileSync("filename.js", options).code;
-```
-
-### to5.transformFile(filename, [opts], callback)
-
-```javascript
-to5.transformFile("filename.js", options, function (err, result) {
-  result.code;
-});
-```
-
-### to5.transform.fromAst(ast, [code], [opts])
-
-```javascript
-var result = to5.transform.fromAst(ast, "var a = 2;", opts);
-result.code;
-result.map;
-result.ast;
-```
-
-#### Options
-
-```javascript
-{
-  // Filename for use in errors etc.
-  // Default: "unknown"
-  filename: "filename",
-
-  // Filename relative to `sourceRoot`
-  // Default: `filename` option.
-  filenameRelative: "",
-
-  // List of transformers to EXCLUDE.
-  // Run `6to5 --help` to see a full list of transformers.
-  blacklist: [],
-
-  // List of transformers to ONLY use.
-  // Run `6to5 --help` to see a full list of transformers.
-  whitelist: [],
-
-  // Module formatter to use
-  // Run `6to5 --help` to see a full list of module formatters.
-  // Default: "common"
-  modules: "common",
-
-  // If truthy, adds a `map` property to returned output.
-  // If set to "inline", a comment with a sourceMappingURL directive is added to
-  // the bottom of the returned code.
-  // Default: false
-  sourceMap: true,
-
-  // Set `file` on returned source map.
-  // Default: `filenameRelative` option.
-  sourceMapName: "filename",
-
-  // Set `sources[0]` on returned source map.
-  // Default: `filenameRelative` option.
-  sourceFileName: "filename",
-
-  // The root from which all sources are relative
-  // Default: `moduleRoot` option.
-  sourceRoot: "assets/scripts",
-
-  // Optional prefix for the AMD module formatter that will be prepend to the
-  // filename on module definitions
-  // Default: `sourceRoot` option.
-  moduleRoot: "my-app",
-
-  // If truthy, insert an explicit id for each defined AMD/System module.
-  // By default, AMD/System modules are anonymous.
-  // Default: false
-  moduleIds: true,
-
-  // Optionally replace all 6to5 helper declarations with a referenece to this
-  // variable. If set to `true` then the default namespace is used "to5Runtime".
-  // Default: false
-  runtime: true,
-
-  // Enable support for experimental ES7 features
-  // Default: false
-  experimental: true,
-
-  // Set this to `false` if you don't want the transformed AST in the returned
-  // result
-  // Default: true
-  ast: true,
-
-  // Set this to `false` if you don't want the transformed code in the returned
-  // result
-  // Default: true
-  code: true,
-
-  format: {
-    // Output comments in generated output
-    // Default: true
-    comments: true,
-
-    // Do not include superfluous whitespace characters and line terminators
-    // Default: false
-    compact: false,
-
-    indent: {
-      // Preserve parentheses in new expressions that have no arguments
-      // Default: true
-      parentheses: true,
-
-      // Adjust the indentation of multiline comments to keep asterisks vertically aligned
-      // Default: true
-      adjustMultilineComment: true,
-
-      // Indent string
-      // Default: "  "
-      style: "  ",
-
-      // Base indent level
-      // Default: 0
-      base: 0
-    }
-  }
-}
-```
-
-### Require hook
-
-All subsequent files required by node with the extensions `.es6` and `.js` will
-be transformed by 6to5. The polyfill specified in [Polyfill](polyfill.md) is
-also required; but this is automatically loaded when using:
-
-Source maps are automatically configured so if any errors a thrown then line
-number info is mapped and you'll get the correct source location.
-
-```javascript
-require("6to5/register");
-```
-
-**NOTE:** By default all requires to `node_modules` will be ignored. You can
-override this by passing an ignore regex via:
-
-```javascript
-require("6to5/register")({
-  // This will override `node_modules` ignoring - you can alternatively pass
-  // a regex
-  ignore: false
-});
-```
-
-**NOTE:** Using 6to5-node or `require("6to5/register")`, 6to5 will check what features are available in the current environment and blacklists them if they're supported.
-
-#### Options
-
-```javascript
-require("6to5/register")({
-  // Optional ignore regex - if any filenames **do** match this regex then they
-  // aren't compiled
-  ignore: /regex/,
-
-  // Optional only regex - if any filenames **don't** match this regex then they
-  // aren't compiled
-  only: /my_es6_folder/,
-
-  // See options above for usage
-  whitelist: [],
-  blacklist: [],
-
-  // This will remove the currently hooked extensions of .es6 and .js so you'll
-  // have to add them back if you want them to be used again.
-  extensions: [".js", ".es6"],
-
-  // Enables `roadrunner` cache that will save to a `.roadrunner.json` file in your cwd
-  // Do not check this into git as it's user-specific
-  cache: true
-});
-```
diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index 73c10aef1f..3d0bf8b4e3 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -10,11 +10,12 @@ var t         = require("./types");
 var _         = require("lodash");
 
 function File(opts) {
-  this.dynamicImports = [];
-  this.opts           = File.normaliseOptions(opts);
-  this.transformers   = this.getTransformers();
-  this.uids           = {};
-  this.ast            = {};
+  this.dynamicImports   = [];
+  this.dynamicImportIds = {};
+  this.opts             = File.normaliseOptions(opts);
+  this.transformers     = this.getTransformers();
+  this.uids             = {};
+  this.ast              = {};
 }
 
 File.helpers = [
@@ -29,12 +30,17 @@ File.helpers = [
   "object-without-properties",
   "has-own",
   "slice",
+  "bind",
   "define-property",
-  "async-to-generator"
+  "async-to-generator",
+  "interop-require-wildcard",
+  "typeof",
+  "exports-wildcard"
 ];
 
 File.excludeHelpersFromRuntime = [
-  "async-to-generator"
+  "async-to-generator",
+  "typeof"
 ];
 
 File.normaliseOptions = function (opts) {
@@ -160,11 +166,20 @@ File.prototype.parseShebang = function (code) {
   return code;
 };
 
-File.prototype.addImport = function (id, source) {
-  var specifiers = [t.importSpecifier(t.identifier("default"), id)];
-  var declar = t.importDeclaration(specifiers, t.literal(source));
-  declar._blockHoist = 3;
-  this.dynamicImports.push(declar);
+File.prototype.addImport = function (source, name) {
+  name = name || source;
+  var id = this.dynamicImportIds[name];
+
+  if (!id) {
+    id = this.dynamicImportIds[name] = this.generateUidIdentifier(name);
+
+    var specifiers = [t.importSpecifier(t.identifier("default"), id)];
+    var declar = t.importDeclaration(specifiers, t.literal(source));
+    declar._blockHoist = 3;
+    this.dynamicImports.push(declar);
+  }
+
+  return id;
 };
 
 File.prototype.addHelper = function (name) {
@@ -273,7 +288,7 @@ File.prototype.generate = function () {
 };
 
 File.prototype.generateUid = function (name, scope) {
-  name = t.toIdentifier(name);
+  name = t.toIdentifier(name).replace(/^_+/, "");
 
   scope = scope || this.scope;
 
diff --git a/lib/6to5/generation/generators/expressions.js b/lib/6to5/generation/generators/expressions.js
index 17f5dbda68..b246abf27f 100644
--- a/lib/6to5/generation/generators/expressions.js
+++ b/lib/6to5/generation/generators/expressions.js
@@ -1,5 +1,6 @@
 var util = require("../../util");
 var t    = require("../../types");
+var _    = require("lodash");
 
 exports.UnaryExpression = function (node, print) {
   var hasSpace = /[a-z]$/.test(node.operator);
@@ -86,6 +87,7 @@ exports.ExpressionStatement = function (node, print) {
 
 exports.BinaryExpression =
 exports.LogicalExpression =
+exports.AssignmentPattern =
 exports.AssignmentExpression = function (node, print) {
   print(node.left);
   this.push(" " + node.operator + " ");
@@ -102,7 +104,12 @@ exports.MemberExpression = function (node, print) {
     throw new TypeError("Got a MemberExpression for MemberExpression property");
   }
 
-  if (node.computed) {
+  var computed = node.computed;
+  if (t.isLiteral(node.property) && _.isNumber(node.property.value)) {
+    computed = true;
+  }
+
+  if (computed) {
     this.push("[");
     print(node.property);
     this.push("]");
diff --git a/lib/6to5/generation/node/index.js b/lib/6to5/generation/node/index.js
index b0b283d853..8828ba9030 100644
--- a/lib/6to5/generation/node/index.js
+++ b/lib/6to5/generation/node/index.js
@@ -61,9 +61,12 @@ Node.prototype.needsParens = function () {
   if (!parent) return false;
 
   if (t.isNewExpression(parent) && parent.callee === node) {
-    return t.isCallExpression(node) || _.some(node, function (val) {
+    if (t.isCallExpression(node)) return true;
+
+    var hasCall = _.some(node, function (val) {
       return t.isCallExpression(val);
     });
+    if (hasCall) return true;
   }
 
   return find(parens, node, parent);
diff --git a/lib/6to5/generation/node/parentheses.js b/lib/6to5/generation/node/parentheses.js
index 6d96d78675..8415b0c9a5 100644
--- a/lib/6to5/generation/node/parentheses.js
+++ b/lib/6to5/generation/node/parentheses.js
@@ -13,7 +13,8 @@ _.each([
   ["<", ">", "<=", ">=", "in", "instanceof"],
   [">>", "<<", ">>>"],
   ["+", "-"],
-  ["*", "/", "%"]
+  ["*", "/", "%"],
+  ["**"]
 ], function (tier, i) {
   _.each(tier, function (op) {
     PRECEDENCE[op] = i;
@@ -35,7 +36,7 @@ exports.ObjectExpression = function (node, parent) {
 };
 
 exports.Binary = function (node, parent) {
-  if (t.isCallExpression(parent) && parent.callee === node) {
+  if ((t.isCallExpression(parent) || t.isNewExpression(parent)) && parent.callee === node) {
     return true;
   }
 
diff --git a/lib/6to5/patch.js b/lib/6to5/patch.js
index 836538b2f8..76e65bd38f 100644
--- a/lib/6to5/patch.js
+++ b/lib/6to5/patch.js
@@ -12,6 +12,12 @@ var types = require("ast-types");
 var def   = types.Type.def;
 var or    = types.Type.or;
 
+def("AssignmentPattern")
+    .bases("Pattern")
+    .build("left", "right")
+    .field("left", def("Pattern"))
+    .field("right", def("Expression"));
+
 // Acorn - Same as ImportNamespaceSpecifier but `id` is `name`
 def("ImportBatchSpecifier")
   .bases("Specifier")
diff --git a/lib/6to5/register.js b/lib/6to5/register.js
index d4538c0ae5..d73532e1e9 100644
--- a/lib/6to5/register.js
+++ b/lib/6to5/register.js
@@ -123,7 +123,7 @@ var hookExtensions = function (_exts) {
   });
 };
 
-hookExtensions([".es6", ".js"]);
+hookExtensions([".es6", ".es", ".js"]);
 
 module.exports = function (opts) {
   // normalise options
diff --git a/lib/6to5/transformation/modules/_default.js b/lib/6to5/transformation/modules/_default.js
index 95b7a97b85..d067eece2a 100644
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -141,10 +141,18 @@ DefaultFormatter.prototype._exportSpecifier = function (getRef, specifier, node,
       // export * from "foo";
       nodes.push(this._exportsWildcard(getRef(), node));
     } else {
+      var ref;
+      if (t.isSpecifierDefault(specifier) && !this.noInteropRequire) {
+        // importing a default so we need to normalise it
+        ref = t.callExpression(this.file.addHelper("interop-require"), [getRef()]);
+      } else {
+        ref = t.memberExpression(getRef(), specifier.id);
+      }
+
       // export { foo } from "test";
       nodes.push(this._exportsAssign(
         t.getSpecifierName(specifier),
-        t.memberExpression(getRef(), specifier.id),
+        ref,
         node
       ));
     }
@@ -155,9 +163,9 @@ DefaultFormatter.prototype._exportSpecifier = function (getRef, specifier, node,
 };
 
 DefaultFormatter.prototype._exportsWildcard = function (objectIdentifier) {
-  return util.template("exports-wildcard", {
-    OBJECT: objectIdentifier
-  }, true);
+  return t.expressionStatement(t.callExpression(this.file.addHelper("exports-wildcard"), [
+    t.callExpression(this.file.addHelper("interop-require-wildcard"), [objectIdentifier])
+  ]));
 };
 
 DefaultFormatter.prototype._exportsAssign = function (id, init) {
diff --git a/lib/6to5/transformation/modules/common.js b/lib/6to5/transformation/modules/common.js
index 71223d8ef7..7364d6a3fd 100644
--- a/lib/6to5/transformation/modules/common.js
+++ b/lib/6to5/transformation/modules/common.js
@@ -32,18 +32,24 @@ CommonJSFormatter.prototype.importSpecifier = function (specifier, node, nodes)
       )
     ]));
   } else {
-    // import foo from "foo";
-
-    var templateName = "require-assign";
-
-    // import * as bar from "foo";
-    if (specifier.type !== "ImportBatchSpecifier") templateName += "-key";
-
-    nodes.push(util.template(templateName, {
-      VARIABLE_NAME: variableName,
-      MODULE_NAME:   node.source,
-      KEY:           specifier.id
-    }));
+    if (specifier.type === "ImportBatchSpecifier") {
+      // import * as bar from "foo";
+      nodes.push(t.variableDeclaration("var", [
+        t.variableDeclarator(
+          variableName,
+          t.callExpression(this.file.addHelper("interop-require-wildcard"), [
+            t.callExpression(t.identifier("require"), [node.source])
+          ])
+        )
+      ]));
+    } else {
+      // import foo from "foo";
+      nodes.push(util.template("require-assign-key", {
+        VARIABLE_NAME: variableName,
+        MODULE_NAME:   node.source,
+        KEY:           specifier.id
+      }));
+    }
   }
 };
 
@@ -65,7 +71,7 @@ CommonJSFormatter.prototype.exportDeclaration = function (node, nodes) {
     // exports = module.exports = VALUE;
     if (this.hasNonDefaultExports) templateName = "exports-default-module-override";
 
-    if (t.isFunction(declar) || !this.hasNonDefaultExports) {
+    if (t.isFunctionDeclaration(declar) || !this.hasNonDefaultExports) {
       assign = util.template(templateName, {
         VALUE: this._pushStatement(declar, nodes)
       }, true);
diff --git a/lib/6to5/transformation/modules/system.js b/lib/6to5/transformation/modules/system.js
index b4f72c6d5b..d8a01218e3 100644
--- a/lib/6to5/transformation/modules/system.js
+++ b/lib/6to5/transformation/modules/system.js
@@ -1,6 +1,7 @@
 module.exports = SystemFormatter;
 
 var AMDFormatter = require("./amd");
+var useStrict    = require("../transformers/use-strict");
 var traverse     = require("../../traverse");
 var util         = require("../../util");
 var t            = require("../../types");
@@ -31,7 +32,7 @@ SystemFormatter.prototype._exportsWildcard = function (objectIdentifier, node) {
   var right = objectIdentifier;
 
   var block = t.blockStatement([
-    this.buildExportCall(leftIdentifier, valIdentifier)
+    t.expressionStatement(this.buildExportCall(leftIdentifier, valIdentifier))
   ]);
 
   return this._addImportSource(t.forInStatement(left, right, block), node);
@@ -170,5 +171,9 @@ SystemFormatter.prototype.transform = function (ast) {
 
   handlerBody.push(returnStatement);
 
+  if (useStrict._has(block)) {
+    handlerBody.unshift(block.body.shift());
+  }
+
   program.body = [runner];
 };
diff --git a/lib/6to5/transformation/templates/bind.js b/lib/6to5/transformation/templates/bind.js
new file mode 100644
index 0000000000..abe1c0668a
--- /dev/null
+++ b/lib/6to5/transformation/templates/bind.js
@@ -0,0 +1 @@
+Function.prototype.bind
diff --git a/lib/6to5/transformation/templates/class-super-constructor-call.js b/lib/6to5/transformation/templates/class-super-constructor-call.js
index c50d3a50cc..c9b822f013 100644
--- a/lib/6to5/transformation/templates/class-super-constructor-call.js
+++ b/lib/6to5/transformation/templates/class-super-constructor-call.js
@@ -1,3 +1,3 @@
-if (SUPER_NAME) {
+if (SUPER_NAME !== null) {
   SUPER_NAME.apply(this, arguments);
 }
diff --git a/lib/6to5/transformation/templates/default-parameter.js b/lib/6to5/transformation/templates/default-parameter.js
new file mode 100644
index 0000000000..74fecfd0f2
--- /dev/null
+++ b/lib/6to5/transformation/templates/default-parameter.js
@@ -0,0 +1 @@
+var VARIABLE_NAME = ARGUMENTS[ARGUMENT_KEY] === undefined ? DEFAULT_VALUE : ARGUMENTS[ARGUMENT_KEY];
diff --git a/lib/6to5/transformation/templates/exports-wildcard.js b/lib/6to5/transformation/templates/exports-wildcard.js
index 26e5b73c7d..fc4db3f90a 100644
--- a/lib/6to5/transformation/templates/exports-wildcard.js
+++ b/lib/6to5/transformation/templates/exports-wildcard.js
@@ -1,5 +1,7 @@
 (function (obj) {
   for (var i in obj) {
-    exports[i] = obj[i];
+    if (exports[i] !== undefined) {
+      exports[i] = obj[i];
+    }
   }
-})(OBJECT);
+})
diff --git a/lib/6to5/transformation/templates/if-undefined-set-to.js b/lib/6to5/transformation/templates/if-undefined-set-to.js
deleted file mode 100644
index c5ed82cdf9..0000000000
--- a/lib/6to5/transformation/templates/if-undefined-set-to.js
+++ /dev/null
@@ -1 +0,0 @@
-if (VARIABLE === undefined) VARIABLE = DEFAULT;
diff --git a/lib/6to5/transformation/templates/inherits.js b/lib/6to5/transformation/templates/inherits.js
index 1e8f6b5e8f..8822bbea7e 100644
--- a/lib/6to5/transformation/templates/inherits.js
+++ b/lib/6to5/transformation/templates/inherits.js
@@ -1,4 +1,7 @@
 (function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
diff --git a/lib/6to5/transformation/templates/interop-require-wildcard.js b/lib/6to5/transformation/templates/interop-require-wildcard.js
new file mode 100644
index 0000000000..89287917c8
--- /dev/null
+++ b/lib/6to5/transformation/templates/interop-require-wildcard.js
@@ -0,0 +1,3 @@
+(function (obj) {
+  return obj && obj.constructor === Object ? obj : { default: obj };
+})
diff --git a/lib/6to5/transformation/templates/object-define-properties-closure.js b/lib/6to5/transformation/templates/object-define-properties-closure.js
new file mode 100644
index 0000000000..a4e51eaf06
--- /dev/null
+++ b/lib/6to5/transformation/templates/object-define-properties-closure.js
@@ -0,0 +1,5 @@
+
+(function (KEY) {
+  CONTENT;
+  return KEY;
+})(OBJECT);
diff --git a/lib/6to5/transformation/templates/require-assign.js b/lib/6to5/transformation/templates/require-assign.js
deleted file mode 100644
index 2b389fbfdf..0000000000
--- a/lib/6to5/transformation/templates/require-assign.js
+++ /dev/null
@@ -1 +0,0 @@
-var VARIABLE_NAME = require(MODULE_NAME);
diff --git a/lib/6to5/transformation/templates/rest.js b/lib/6to5/transformation/templates/rest.js
new file mode 100644
index 0000000000..f396f01117
--- /dev/null
+++ b/lib/6to5/transformation/templates/rest.js
@@ -0,0 +1,3 @@
+for (var KEY = START; KEY < ARGUMENTS.length; KEY++) {
+  ARRAY[ARRAY_KEY] = ARGUMENTS[KEY];
+}
diff --git a/lib/6to5/transformation/templates/typeof.js b/lib/6to5/transformation/templates/typeof.js
new file mode 100644
index 0000000000..8efdeefe3d
--- /dev/null
+++ b/lib/6to5/transformation/templates/typeof.js
@@ -0,0 +1,3 @@
+(function (obj) {
+  return obj && obj.constructor === Symbol ? "symbol" : typeof obj;
+});
diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index e78a0ea3b1..7a5a36fa77 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -39,11 +39,6 @@ transform.moduleFormatters = {
 };
 
 _.each({
-  // spec
-  specBlockHoistFunctions:   require("./transformers/spec-block-hoist-functions"),
-  specNoForInOfAssignment:   require("./transformers/spec-no-for-in-of-assignment"),
-  specNoDuplicateProperties: require("./transformers/spec-no-duplicate-properties"),
-
   // playground
   methodBinding:             require("./transformers/playground-method-binding"),
   memoizationOperator:       require("./transformers/playground-memoization-operator"),
@@ -86,10 +81,11 @@ _.each({
   _declarations:             require("./transformers/_declarations"),
 
   // wrap up
+  useStrict:                 require("./transformers/use-strict"),
   _aliasFunctions:           require("./transformers/_alias-functions"),
   _moduleFormatter:          require("./transformers/_module-formatter"),
-  useStrict:                 require("./transformers/use-strict"),
 
+  typeofSymbol:              require("./transformers/optional-typeof-symbol"),
   coreAliasing:              require("./transformers/optional-core-aliasing"),
   undefinedToVoid:           require("./transformers/optional-undefined-to-void"),
 
diff --git a/lib/6to5/transformation/transformer.js b/lib/6to5/transformation/transformer.js
index 7239e5e976..d9587a38c0 100644
--- a/lib/6to5/transformation/transformer.js
+++ b/lib/6to5/transformation/transformer.js
@@ -8,20 +8,25 @@ function Transformer(key, transformer, opts) {
   this.manipulateOptions = transformer.manipulateOptions;
   this.experimental      = !!transformer.experimental;
   this.secondPass        = !!transformer.secondPass;
-  this.transformer       = Transformer.normalise(transformer);
+  this.transformer       = this.normalise(transformer);
   this.optional          = !!transformer.optional;
   this.opts              = opts || {};
   this.key               = key;
 }
 
-Transformer.normalise = function (transformer) {
+Transformer.prototype.normalise = function (transformer) {
+  var self = this;
+
   if (_.isFunction(transformer)) {
     transformer = { ast: transformer };
   }
 
   _.each(transformer, function (fns, type) {
     // hidden property
-    if (type[0] === "_") return;
+    if (type[0] === "_") {
+      self[type] = fns;
+      return;
+    }
 
     if (_.isFunction(fns)) fns = { enter: fns };
 
diff --git a/lib/6to5/transformation/transformers/_alias-functions.js b/lib/6to5/transformation/transformers/_alias-functions.js
index 2230a44e9a..5cf9003c84 100644
--- a/lib/6to5/transformation/transformers/_alias-functions.js
+++ b/lib/6to5/transformation/transformers/_alias-functions.js
@@ -67,7 +67,7 @@ var go = function (getBody, node, file, scope) {
   }
 
   if (thisId) {
-    pushDeclaration(thisId, t.identifier("this"));
+    pushDeclaration(thisId, t.thisExpression());
   }
 };
 
diff --git a/lib/6to5/transformation/transformers/_block-hoist.js b/lib/6to5/transformation/transformers/_block-hoist.js
index b6fff4a860..e024a8a193 100644
--- a/lib/6to5/transformation/transformers/_block-hoist.js
+++ b/lib/6to5/transformation/transformers/_block-hoist.js
@@ -1,4 +1,5 @@
-var _ = require("lodash");
+var useStrict = require("./use-strict");
+var _         = require("lodash");
 
 // Priority:
 //
@@ -17,13 +18,15 @@ exports.Program = {
     }
     if (!hasChange) return;
 
-    var nodePriorities = _.groupBy(node.body, function (bodyNode) {
-      var priority = bodyNode._blockHoist;
-      if (priority == null) priority = 1;
-      if (priority === true) priority = 2;
-      return priority;
-    });
+    useStrict._wrap(node, function () {
+      var nodePriorities = _.groupBy(node.body, function (bodyNode) {
+        var priority = bodyNode._blockHoist;
+        if (priority == null) priority = 1;
+        if (priority === true) priority = 2;
+        return priority;
+      });
 
-    node.body = _.flatten(_.values(nodePriorities).reverse());
+      node.body = _.flatten(_.values(nodePriorities).reverse());
+    });
   }
 };
diff --git a/lib/6to5/transformation/transformers/_declarations.js b/lib/6to5/transformation/transformers/_declarations.js
index ae0f355b08..20fbfadb6e 100644
--- a/lib/6to5/transformation/transformers/_declarations.js
+++ b/lib/6to5/transformation/transformers/_declarations.js
@@ -1,4 +1,5 @@
-var t = require("../../types");
+var useStrict = require("./use-strict");
+var t         = require("../../types");
 
 exports.secondPass = true;
 
@@ -7,23 +8,25 @@ exports.Program = function (node) {
   var kinds = {};
   var kind;
 
-  for (var i in node._declarations) {
-    var declar = node._declarations[i];
+  useStrict._wrap(node, function () {
+    for (var i in node._declarations) {
+      var declar = node._declarations[i];
 
-    kind = declar.kind || "var";
-    var declarNode = t.variableDeclarator(declar.id, declar.init);
+      kind = declar.kind || "var";
+      var declarNode = t.variableDeclarator(declar.id, declar.init);
 
-    if (!declar.init) {
-      kinds[kind] = kinds[kind] || [];
-      kinds[kind].push(declarNode);
-    } else {
-      node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+      if (!declar.init) {
+        kinds[kind] = kinds[kind] || [];
+        kinds[kind].push(declarNode);
+      } else {
+        node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+      }
     }
-  }
 
-  for (kind in kinds) {
-    node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
-  }
+    for (kind in kinds) {
+      node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
+    }
+  });
 
   node._declarations = null;
 };
diff --git a/lib/6to5/transformation/transformers/es6-default-parameters.js b/lib/6to5/transformation/transformers/es6-default-parameters.js
index 9715c2bbdc..ba3c0ad631 100644
--- a/lib/6to5/transformation/transformers/es6-default-parameters.js
+++ b/lib/6to5/transformation/transformers/es6-default-parameters.js
@@ -49,16 +49,29 @@ exports.Function = function (node, parent, file, scope) {
 
   var body = [];
 
+  var argsIdentifier = t.identifier("arguments");
+  argsIdentifier._ignoreAliasFunctions = true;
+
+  var lastNonDefaultParam = 0;
+
   for (i in node.defaults) {
     def = node.defaults[i];
-    if (!def) continue;
+    if (!def) {
+      lastNonDefaultParam = +i + 1;
+      continue;
+    }
 
-    body.push(util.template("if-undefined-set-to", {
-      VARIABLE: node.params[i],
-      DEFAULT:  def
+    body.push(util.template("default-parameter", {
+      VARIABLE_NAME: node.params[i],
+      DEFAULT_VALUE: def,
+      ARGUMENT_KEY:  t.literal(+i),
+      ARGUMENTS:     argsIdentifier
     }, true));
   }
 
+  // we need to cut off all trailing default parameters
+  node.params = node.params.slice(0, lastNonDefaultParam);
+
   if (iife) {
     var container = t.functionExpression(null, [], node.body, node.generator);
     container._aliasFunction = true;
diff --git a/lib/6to5/transformation/transformers/es6-destructuring.js b/lib/6to5/transformation/transformers/es6-destructuring.js
index c8b7bffb36..489d2de53c 100644
--- a/lib/6to5/transformation/transformers/es6-destructuring.js
+++ b/lib/6to5/transformation/transformers/es6-destructuring.js
@@ -20,11 +20,31 @@ var push = function (opts, nodes, elem, parentId) {
     pushObjectPattern(opts, nodes, elem, parentId);
   } else if (t.isArrayPattern(elem)) {
     pushArrayPattern(opts, nodes, elem, parentId);
+  } else if (t.isAssignmentPattern(elem)) {
+    pushAssignmentPattern(opts, nodes, elem, parentId);
   } else {
     nodes.push(buildVariableAssign(opts, elem, parentId));
   }
 };
 
+var pushAssignmentPattern = function (opts, nodes, pattern, parentId) {
+  var tempParentId = opts.scope.generateUidBasedOnNode(parentId, opts.file);
+
+  nodes.push(t.variableDeclaration("var", [
+    t.variableDeclarator(tempParentId, parentId)
+  ]));
+
+  nodes.push(buildVariableAssign(
+    opts,
+    pattern.left,
+    t.conditionalExpression(
+      t.binaryExpression("===", tempParentId, t.identifier("undefined")),
+      pattern.right,
+      tempParentId
+    )
+  ));
+};
+
 var pushObjectPattern = function (opts, nodes, pattern, parentId) {
   for (var i in pattern.properties) {
     var prop = pattern.properties[i];
@@ -48,6 +68,8 @@ var pushObjectPattern = function (opts, nodes, pattern, parentId) {
         var value = t.callExpression(opts.file.addHelper("object-without-properties"), [parentId, keys]);
         nodes.push(buildVariableAssign(opts, prop.argument, value));
     } else {
+      if (t.isLiteral(prop.key)) prop.computed = true;
+
       var pattern2   = prop.value;
       var patternId2 = t.memberExpression(parentId, prop.key, prop.computed);
 
@@ -183,6 +205,24 @@ exports.Function = function (node, parent, file, scope) {
   block.body = nodes.concat(block.body);
 };
 
+exports.CatchClause = function (node, parent, file, scope) {
+  var pattern = node.param;
+  if (!t.isPattern(pattern)) return;
+
+  var ref = file.generateUidIdentifier("ref", scope);
+  node.param = ref;
+
+  var nodes = [];
+
+  push({
+    kind: "var",
+    file: file,
+    scope: scope
+  }, nodes, pattern, ref);
+
+  node.body.body = nodes.concat(node.body.body);
+};
+
 exports.ExpressionStatement = function (node, parent, file, scope) {
   var expr = node.expression;
   if (expr.type !== "AssignmentExpression") return;
diff --git a/lib/6to5/transformation/transformers/es6-let-scoping.js b/lib/6to5/transformation/transformers/es6-let-scoping.js
index 3da1800688..44151d58b8 100644
--- a/lib/6to5/transformation/transformers/es6-let-scoping.js
+++ b/lib/6to5/transformation/transformers/es6-let-scoping.js
@@ -376,7 +376,7 @@ LetScoping.prototype.getLetReferences = function () {
 
             // this scope has a variable with the same name so it couldn't belong
             // to our let scope
-            if (scope.hasOwn(node.name)) return;
+            if (scope.hasOwn(node.name, true)) return;
 
             closurify = true;
 
@@ -388,8 +388,6 @@ LetScoping.prototype.getLetReferences = function () {
           }
         });
 
-        return this.skip();
-      } else if (t.isLoop(node)) {
         return this.skip();
       }
     }
diff --git a/lib/6to5/transformation/transformers/es6-rest-parameters.js b/lib/6to5/transformation/transformers/es6-rest-parameters.js
index 37a32657dd..266b6f62f7 100644
--- a/lib/6to5/transformation/transformers/es6-rest-parameters.js
+++ b/lib/6to5/transformation/transformers/es6-rest-parameters.js
@@ -1,4 +1,5 @@
-var t = require("../../types");
+var util = require("../../util");
+var t    = require("../../types");
 
 exports.Function = function (node, parent, file) {
   if (!node.rest) return;
@@ -8,15 +9,28 @@ exports.Function = function (node, parent, file) {
 
   t.ensureBlock(node);
 
-  var call = file.toArray(t.identifier("arguments"));
+  var argsId = t.identifier("arguments");
+  argsId._ignoreAliasFunctions = true;
 
+  var start = t.literal(node.params.length);
+  var key = file.generateUidIdentifier("key");
+
+  var arrKey = key;
   if (node.params.length) {
-    call.arguments.push(t.literal(node.params.length));
+    arrKey = t.binaryExpression("-", arrKey, start);
   }
 
-  call._ignoreAliasFunctions = true;
+  node.body.body.unshift(
+    t.variableDeclaration("var", [
+      t.variableDeclarator(rest, t.arrayExpression([]))
+    ]),
 
-  node.body.body.unshift(t.variableDeclaration("var", [
-    t.variableDeclarator(rest, call)
-  ]));
+    util.template("rest", {
+      ARGUMENTS: argsId,
+      ARRAY_KEY: arrKey,
+      START: start,
+      ARRAY: rest,
+      KEY: key
+    })
+  );
 };
diff --git a/lib/6to5/transformation/transformers/es6-spread.js b/lib/6to5/transformation/transformers/es6-spread.js
index 8c5c008651..5a7b031ce1 100644
--- a/lib/6to5/transformation/transformers/es6-spread.js
+++ b/lib/6to5/transformation/transformers/es6-spread.js
@@ -1,4 +1,5 @@
 var t = require("../../types");
+var _ = require("lodash");
 
 var getSpreadLiteral = function (spread, file) {
   return file.toArray(spread.argument);
@@ -58,7 +59,7 @@ exports.CallExpression = function (node, parent, file, scope) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
-  var contextLiteral = t.literal(null);
+  var contextLiteral = t.identifier("undefined");
 
   node.arguments = [];
 
@@ -83,6 +84,8 @@ exports.CallExpression = function (node, parent, file, scope) {
     if (temp) {
       callee.object = t.assignmentExpression("=", temp, callee.object);
       contextLiteral = temp;
+    } else {
+      contextLiteral = callee.object;
     }
     t.appendToMemberExpression(callee, t.identifier("apply"));
   } else {
@@ -96,7 +99,14 @@ exports.NewExpression = function (node, parent, file) {
   var args = node.arguments;
   if (!hasSpread(args)) return;
 
+  var nativeType = t.isIdentifier(node.callee) && _.contains(t.NATIVE_TYPE_NAMES, node.callee.name);
+
   var nodes = build(args, file);
+
+  if (nativeType) {
+    nodes.unshift(t.arrayExpression([t.literal(null)]));
+  }
+
   var first = nodes.shift();
 
   if (nodes.length) {
@@ -105,5 +115,15 @@ exports.NewExpression = function (node, parent, file) {
     args = first;
   }
 
-  return t.callExpression(file.addHelper("apply-constructor"), [node.callee, args]);
+  if (nativeType) {
+    return t.newExpression(
+      t.callExpression(
+        t.memberExpression(file.addHelper("bind"), t.identifier("apply")),
+        [node.callee, args]
+      ),
+      []
+    );
+  } else {
+    return t.callExpression(file.addHelper("apply-constructor"), [node.callee, args]);
+  }
 };
diff --git a/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js b/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
index beb19dad7a..cda714330c 100644
--- a/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
+++ b/lib/6to5/transformation/transformers/optional-bluebird-coroutines.js
@@ -38,8 +38,6 @@ exports._Function = function (node, callId) {
 exports.Function = function (node, parent, file) {
   if (!node.async || node.generator) return;
 
-  var id = t.identifier("Bluebird");
-  file.addImport(id, "bluebird");
-
+  var id = file.addImport("bluebird");
   return exports._Function(node, t.memberExpression(id, t.identifier("coroutine")));
 };
diff --git a/lib/6to5/transformation/transformers/optional-core-aliasing.js b/lib/6to5/transformation/transformers/optional-core-aliasing.js
index bd2fb2f572..a67bf045ec 100644
--- a/lib/6to5/transformation/transformers/optional-core-aliasing.js
+++ b/lib/6to5/transformation/transformers/optional-core-aliasing.js
@@ -12,8 +12,7 @@ exports.optional = true;
 
 exports.ast = {
   enter: function (ast, file) {
-    file._coreId = file.generateUidIdentifier("core");
-    file.addImport(file._coreId, "core-js/library");
+    file._coreId = file.addImport("core-js/library", "core");
   },
 
   exit: function (ast, file) {
diff --git a/lib/6to5/transformation/transformers/optional-typeof-symbol.js b/lib/6to5/transformation/transformers/optional-typeof-symbol.js
new file mode 100644
index 0000000000..55be121b08
--- /dev/null
+++ b/lib/6to5/transformation/transformers/optional-typeof-symbol.js
@@ -0,0 +1,9 @@
+var t = require("../../types");
+
+exports.optional = true;
+
+exports.UnaryExpression = function (node, parent, file) {
+  if (node.operator === "typeof") {
+    return t.callExpression(file.addHelper("typeof"), [node.argument]);
+  }
+};
diff --git a/lib/6to5/transformation/transformers/spec-block-hoist-functions.js b/lib/6to5/transformation/transformers/spec-block-hoist-functions.js
deleted file mode 100644
index 8d18464de0..0000000000
--- a/lib/6to5/transformation/transformers/spec-block-hoist-functions.js
+++ /dev/null
@@ -1,18 +0,0 @@
-var t = require("../../types");
-
-exports.BlockStatement = function (node, parent) {
-  if (t.isFunction(parent)) return;
-
-  node.body = node.body.map(function (node) {
-    if (t.isFunction(node)) {
-      node.type = "FunctionExpression";
-      var declar = t.variableDeclaration("let", [
-        t.variableDeclarator(node.id, node)
-      ]);
-      declar._blockHoist = true;
-      return declar;
-    } else {
-      return node;
-    }
-  });
-};
diff --git a/lib/6to5/transformation/transformers/spec-member-expression-literals.js b/lib/6to5/transformation/transformers/spec-member-expression-literals.js
index d1c58414d7..6803865073 100644
--- a/lib/6to5/transformation/transformers/spec-member-expression-literals.js
+++ b/lib/6to5/transformation/transformers/spec-member-expression-literals.js
@@ -1,5 +1,4 @@
-var esutils = require("esutils");
-var t       = require("../../types");
+var t = require("../../types");
 
 exports.MemberExpression = function (node) {
   var prop = node.property;
@@ -7,7 +6,7 @@ exports.MemberExpression = function (node) {
     // computed literal that is a valid identifier
     node.property = t.identifier(prop.value);
     node.computed = false;
-  } else if (!node.computed && t.isIdentifier(prop) && esutils.keyword.isKeywordES6(prop.name, true)) {
+  } else if (!node.computed && t.isIdentifier(prop) && !t.isValidIdentifier(prop.name)) {
     node.property = t.literal(prop.name);
     node.computed = true;
   }
diff --git a/lib/6to5/transformation/transformers/spec-no-duplicate-properties.js b/lib/6to5/transformation/transformers/spec-no-duplicate-properties.js
deleted file mode 100644
index 6c7e93e761..0000000000
--- a/lib/6to5/transformation/transformers/spec-no-duplicate-properties.js
+++ /dev/null
@@ -1,25 +0,0 @@
-var t = require("../../types");
-
-exports.ObjectExpression = function (node, parent, file) {
-  var keys = [];
-
-  for (var i in node.properties) {
-    var prop = node.properties[i];
-    if (prop.computed || prop.kind !== "init") continue;
-
-    var key = prop.key;
-    if (t.isIdentifier(key)) {
-      key = key.name;
-    } else if (t.isLiteral(key)) {
-      key = key.value;
-    } else {
-      continue;
-    }
-
-    if (keys.indexOf(key) >= 0) {
-      throw file.errorWithNode(prop.key, "Duplicate property key");
-    } else {
-      keys.push(key);
-    }
-  }
-};
diff --git a/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js b/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js
deleted file mode 100644
index 5af12108f1..0000000000
--- a/lib/6to5/transformation/transformers/spec-no-for-in-of-assignment.js
+++ /dev/null
@@ -1,10 +0,0 @@
-var t = require("../../types");
-
-exports.ForInStatement =
-exports.ForOfStatement = function (node, parent, file) {
-  var left = node.left;
-  if (t.isVariableDeclaration(left)) {
-    var declar = left.declarations[0];
-    if (declar.init) throw file.errorWithNode(declar, "No assignments allowed in for-in/of head");
-  }
-};
diff --git a/lib/6to5/transformation/transformers/spec-property-literals.js b/lib/6to5/transformation/transformers/spec-property-literals.js
index dff7244d1d..f750fa7527 100644
--- a/lib/6to5/transformation/transformers/spec-property-literals.js
+++ b/lib/6to5/transformation/transformers/spec-property-literals.js
@@ -1,5 +1,4 @@
-var esutils = require("esutils");
-var t       = require("../../types");
+var t = require("../../types");
 
 exports.Property = function (node) {
   var key = node.key;
@@ -7,7 +6,7 @@ exports.Property = function (node) {
     // property key is a literal but a valid identifier
     node.key = t.identifier(key.value);
     node.computed = false;
-  } else if (!node.computed && t.isIdentifier(key) && esutils.keyword.isKeywordES6(key.name, true)) {
+  } else if (!node.computed && t.isIdentifier(key) && !t.isValidIdentifier(key.name)) {
     // property key is a keyword
     node.key = t.literal(key.name);
   }
diff --git a/lib/6to5/transformation/transformers/use-strict.js b/lib/6to5/transformation/transformers/use-strict.js
index 02d4dbc264..bd9fd9c651 100644
--- a/lib/6to5/transformation/transformers/use-strict.js
+++ b/lib/6to5/transformation/transformers/use-strict.js
@@ -1,14 +1,27 @@
 var t = require("../../types");
 
+exports._has = function (node) {
+  var first = node.body[0];
+  return t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" });
+};
+
+exports._wrap = function (node, callback) {
+  var useStrictNode;
+  if (exports._has(node)) {
+    useStrictNode = node.body.shift();
+  }
+
+  callback();
+
+  if (useStrictNode) {
+    node.body.unshift(useStrictNode);
+  }
+};
+
 exports.ast = {
   exit: function (ast) {
-    var body = ast.program.body;
-    var first = body[0];
-
-    var noStrict = !first || !t.isExpressionStatement(first) || !t.isLiteral(first.expression) || first.expression.value !== "use strict";
-
-    if (noStrict) {
-      body.unshift(t.expressionStatement(t.literal("use strict")));
+    if (!exports._has(ast.program)) {
+      ast.program.body.unshift(t.expressionStatement(t.literal("use strict")));
     }
   }
 };
diff --git a/lib/6to5/traverse/scope.js b/lib/6to5/traverse/scope.js
index f6cc050998..eaa82a51b2 100644
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traverse/scope.js
@@ -63,38 +63,29 @@ Scope.prototype.generateUidBasedOnNode = function (parent, file) {
     node = parent.left;
   } else if (t.isVariableDeclarator(parent)) {
     node = parent.id;
-  }
-
-  var id = "ref";
-
-  if (t.isProperty(node)) {
+  } else if (t.isProperty(node)) {
     node = node.key;
   }
 
-  if (t.isIdentifier(node)) {
-    id = node.name;
-  } else if (t.isLiteral(node)) {
-    id = node.value;
-  } else if (t.isMemberExpression(node)) {
-    var parts = [];
+  var parts = [];
 
-    var add = function (node) {
-      if (t.isMemberExpression(node)) {
-        add(node.object);
-        add(node.property);
-      } else if (t.isIdentifier(node)) {
-        parts.push(node.name);
-      } else if (t.isLiteral(node)) {
-        parts.push(node.value);
-      }
-    };
+  var add = function (node) {
+    if (t.isMemberExpression(node)) {
+      add(node.object);
+      add(node.property);
+    } else if (t.isIdentifier(node)) {
+      parts.push(node.name);
+    } else if (t.isLiteral(node)) {
+      parts.push(node.value);
+    } else if (t.isCallExpression(node)) {
+      add(node.callee);
+    }
+  };
 
-    add(node);
+  add(node);
 
-    id = parts.join("$");
-  }
-
-  id = id.replace(/^_/, "");
+  var id = parts.join("$");
+  id = id.replace(/^_/, "") || "ref";
 
   return file.generateUidIdentifier(id, this);
 };
@@ -108,10 +99,6 @@ Scope.prototype.generateUidBasedOnNode = function (parent, file) {
  */
 
 Scope.prototype.generateTempBasedOnNode = function (node, file) {
-  if (!t.isIdentifier(node) && !t.isMemberExpression(node)) {
-    throw new TypeError("Invalid node type " + JSON.stringify(node.type) + " passed to Scope.prototype.generateTempBasedOnNode");
-  }
-
   if (t.isIdentifier(node) && this.has(node.name, true)) {
     return null;
   }
diff --git a/lib/6to5/types/alias-keys.json b/lib/6to5/types/alias-keys.json
index 56ad154225..e07ecc429d 100644
--- a/lib/6to5/types/alias-keys.json
+++ b/lib/6to5/types/alias-keys.json
@@ -39,8 +39,9 @@
   "ForInStatement": ["Statement", "For", "Scope", "Loop"],
   "ForStatement":   ["Statement", "For", "Scope", "Loop"],
 
-  "ObjectPattern": ["Pattern"],
-  "ArrayPattern":  ["Pattern"],
+  "ObjectPattern":     ["Pattern"],
+  "ArrayPattern":      ["Pattern"],
+  "AssignmentPattern": ["Pattern"],
 
   "Property": ["UserWhitespacable"],
   "XJSElement": ["UserWhitespacable", "Expression"],
diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index 284fb7eb12..e1f0b9ec90 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -3,6 +3,10 @@ var _       = require("lodash");
 
 var t = exports;
 
+t.NATIVE_TYPE_NAMES = ["Array", "Object", "Number", "Boolean", "Date", "Array", "String"];
+
+//
+
 var addAssert = function (type, is) {
   t["assert" + type] = function (node, opts) {
     opts = opts || {};
@@ -214,7 +218,7 @@ t.isReferenced = function (node, parent) {
  */
 
 t.isValidIdentifier = function (name) {
-  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isKeywordES6(name, true);
+  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isReservedWordES6(name, true);
 };
 
 /*
@@ -227,6 +231,8 @@ t.isValidIdentifier = function (name) {
 t.toIdentifier = function (name) {
   if (t.isIdentifier(name)) return name.name;
 
+  name = name + "";
+
   // replace all non-valid identifiers with dashes
   name = name.replace(/[^a-zA-Z0-9$_]/g, "-");
 
@@ -241,6 +247,10 @@ t.toIdentifier = function (name) {
   // remove underscores from start of name
   name = name.replace(/^\_/, "");
 
+  if (!t.isValidIdentifier(name)) {
+    name = "_" + name;
+  }
+
   return name || '_';
 };
 
diff --git a/lib/6to5/types/visitor-keys.json b/lib/6to5/types/visitor-keys.json
index 32292aa669..aac62dd391 100644
--- a/lib/6to5/types/visitor-keys.json
+++ b/lib/6to5/types/visitor-keys.json
@@ -3,6 +3,7 @@
   "ArrayPattern":              ["elements"],
   "ArrowFunctionExpression":   ["params", "defaults", "rest", "body"],
   "AssignmentExpression":      ["left", "right"],
+  "AssignmentPattern":         ["left", "right"],
   "AwaitExpression":           ["argument"],
   "BinaryExpression":          ["left", "right"],
   "BindFunctionExpression":    ["callee", "arguments"],
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 033fa3c3bb..c291d12abd 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -12,7 +12,7 @@ var _          = require("lodash");
 exports.inherits = util.inherits;
 
 exports.canCompile = function (filename, altExts) {
-  var exts = altExts || [".js", ".jsx", ".es6"];
+  var exts = altExts || [".js", ".jsx", ".es6", ".es"];
   var ext = path.extname(filename);
   return _.contains(exts, ext);
 };
diff --git a/package.json b/package.json
index b6068f2962..bd0c506c62 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "6to5",
   "description": "Turn ES6 code into readable vanilla ES5 with source maps",
-  "version": "2.4.10",
+  "version": "2.6.3",
   "author": "Sebastian McKenzie <sebmck@gmail.com>",
   "homepage": "https://github.com/6to5/6to5",
   "repository": {
@@ -39,19 +39,20 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-6to5": "0.11.1-8",
+    "acorn-6to5": "0.11.1-11",
     "ast-types": "~0.6.1",
     "chokidar": "0.11.1",
     "commander": "2.5.0",
-    "core-js": "^0.3.3",
+    "core-js": "^0.4.0",
     "estraverse": "1.8.0",
     "esutils": "1.1.6",
+    "esvalid": "^1.1.0",
     "fs-readdir-recursive": "0.1.0",
     "jshint": "^2.5.10",
     "lodash": "2.4.1",
     "mkdirp": "0.5.0",
     "private": "0.1.6",
-    "regenerator": "^0.8.2",
+    "regenerator": "^0.8.3",
     "regexpu": "0.3.0",
     "roadrunner": "^1.0.4",
     "source-map": "0.1.40",
diff --git a/test/_helper.js b/test/_helper.js
index a988f30d73..60371d0e2f 100644
--- a/test/_helper.js
+++ b/test/_helper.js
@@ -1,8 +1,9 @@
-var fs = require("fs");
-var _  = require("lodash");
+var path = require("path");
+var fs   = require("fs");
+var _    = require("lodash");
 
 var humanise = function (val) {
-  return val.replace(/-/g, " ");
+  return path.basename(val, path.extname(val)).replace(/-/g, " ");
 };
 
 var readFile = exports.readFile = function (filename) {
@@ -15,11 +16,11 @@ var readFile = exports.readFile = function (filename) {
   }
 };
 
-exports.get = function (entryName) {
+exports.get = function (entryName, entryLoc) {
   if (exports.cache[entryName]) return exports.cache[entryName];
 
   var suites = [];
-  var entryLoc = __dirname + "/fixtures/" + entryName;
+  var entryLoc = entryLoc || __dirname + "/fixtures/" + entryName;
 
   _.each(fs.readdirSync(entryLoc), function (suiteName) {
     if (suiteName[0] === ".") return;
@@ -35,9 +36,18 @@ exports.get = function (entryName) {
     var suiteOptsLoc = suite.filename + "/options.json";
     if (fs.existsSync(suiteOptsLoc)) suite.options = require(suiteOptsLoc);
 
-    _.each(fs.readdirSync(suite.filename), function (taskName) {
-      var taskDir = suite.filename + "/" + taskName;
-      if (fs.statSync(taskDir).isFile()) return;
+    if (fs.statSync(suite.filename).isFile()) {
+      push(suiteName, suite.filename);
+    } else {
+      _.each(fs.readdirSync(suite.filename), function (taskName) {
+        var taskDir = suite.filename + "/" + taskName;
+        push(taskName, taskDir);
+      });
+    }
+
+    function push(taskName, taskDir) {
+      // tracuer error tests
+      if (taskName.indexOf("Error_") >= 0) return;
 
       var actualLocAlias = suiteName + "/" + taskName + "/actual.js";
       var expectLocAlias = suiteName + "/" + taskName + "/expected.js";
@@ -47,6 +57,13 @@ exports.get = function (entryName) {
       var expectLoc = taskDir + "/expected.js";
       var execLoc   = taskDir + "/exec.js";
 
+      if (fs.statSync(taskDir).isFile()) {
+        var ext = path.extname(taskDir);
+        if (ext !== ".js" && ext !== ".module.js") return;
+
+        execLoc = taskDir;
+      }
+
       var taskOpts = _.merge({
         filenameRelative: expectLocAlias,
         sourceFileName:   actualLocAlias,
@@ -77,6 +94,18 @@ exports.get = function (entryName) {
         }
       };
 
+      // traceur checks
+
+      var shouldSkip = function (code) {
+        return code.indexOf("// Error:") >= 0 || code.indexOf("// Skip.") >= 0;
+      };
+
+      if (shouldSkip(test.actual.code) || shouldSkip(test.exec.code)) {
+        return;
+      } else if (test.exec.code.indexOf("// Async.") >= 0) {
+        //test.options.asyncExec = true;
+      }
+
       suite.tests.push(test);
 
       var sourceMappingsLoc = taskDir + "/source-mappings.json";
@@ -90,7 +119,7 @@ exports.get = function (entryName) {
         test.options.sourceMap = true;
         test.sourceMap = require(sourceMap);
       }
-    });
+    }
   });
 
   return exports.cache[entryName] = suites;
@@ -104,4 +133,5 @@ try {
   var cache = exports.cache = {};
   cache.transformation = exports.get("transformation");
   cache.generation     = exports.get("generation");
+  cache.esnext         = exports.get("esnext");
 }
diff --git a/test/_transformation-helper.js b/test/_transformation-helper.js
new file mode 100644
index 0000000000..db754ac9ec
--- /dev/null
+++ b/test/_transformation-helper.js
@@ -0,0 +1,168 @@
+var genHelpers = require("./_generator-helpers");
+var transform  = require("../lib/6to5/transformation/transform");
+var sourceMap  = require("source-map");
+var esvalid    = require("esvalid");
+var Module     = require("module");
+var helper     = require("./_helper");
+var assert     = require("assert");
+var chai       = require("chai");
+var path       = require("path");
+var util       = require("../lib/6to5/util");
+var _          = require("lodash");
+
+require("../lib/6to5/polyfill");
+
+global.assertNoOwnProperties = function (obj) {
+  assert.equal(Object.getOwnPropertyNames(obj).length, 0);
+};
+
+global.assertArrayEquals = assert.deepEqual;
+global.assert = chai.assert;
+global.chai = chai;
+global.genHelpers = genHelpers;
+
+// Different Traceur generator message
+chai.assert._throw = chai.assert.throw;
+chai.assert.throw = function (fn, msg) {
+  if (msg === '"throw" on executing generator' ||
+      msg === '"next" on executing generator') {
+    msg = "Generator is already running";
+  } else if (msg === "Sent value to newborn generator") {
+    msg = /^attempt to send (.*?) to newborn generator$/;
+  }
+
+  return chai.assert._throw(fn, msg);
+};
+
+var run = function (task, done) {
+  var actual = task.actual;
+  var expect = task.expect;
+  var exec   = task.exec;
+  var opts   = task.options;
+
+  var getOpts = function (self) {
+    return _.merge({
+      filename: self.loc
+    }, opts);
+  };
+
+  var execCode = exec.code;
+  var result;
+
+  var checkAst = function (result) {
+    if (opts.noCheckAst) return;
+
+    var errors = esvalid.errors(result.ast.program);
+    if (errors.length) {
+      var msg = [];
+      _.each(errors, function (err) {
+        msg.push(err.message + " - " + JSON.stringify(err.node));
+      });
+      throw new Error(msg.join(". "));
+    }
+  };
+
+  if (execCode) {
+    result = transform(execCode, getOpts(exec));
+    checkAst(result);
+    execCode = result.code;
+
+    try {
+      var fakeRequire = function (loc) {
+        if (loc === "../../../src/runtime/polyfills/Number.js") {
+          return Number;
+        } else if (loc === "../../../src/runtime/polyfills/Math.js") {
+          return Math;
+        } else {
+          return require(path.resolve(exec.loc, "..", loc));
+        }
+      };
+
+      var fn = new Function("require", "done", execCode);
+      fn.call(global, fakeRequire, chai.assert, done);
+    } catch (err) {
+      err.message = exec.loc + ": " + err.message;
+      err.message += util.codeFrame(execCode);
+      throw err;
+    }
+  }
+
+  var actualCode = actual.code;
+  var expectCode = expect.code;
+  if (!execCode || actualCode) {
+    result     = transform(actualCode, getOpts(actual));
+    checkAst(result);
+    actualCode = result.code;
+
+    chai.expect(actualCode).to.be.equal(expectCode, actual.loc + " !== " + expect.loc);
+  }
+
+  if (task.sourceMap) {
+    chai.expect(result.map).to.deep.equal(task.sourceMap);
+  }
+
+  if (task.sourceMappings) {
+    var consumer = new sourceMap.SourceMapConsumer(result.map);
+
+    _.each(task.sourceMappings, function (mapping, i) {
+      var expect = mapping.original;
+
+      var actual = consumer.originalPositionFor(mapping.generated);
+      chai.expect({ line: actual.line, column: actual.column }).to.deep.equal(expect);
+    });
+  }
+};
+
+module.exports = function (suiteOpts, taskOpts, dynamicOpts) {
+  taskOpts = taskOpts || {};
+
+  require("../register")(taskOpts);
+
+  _.each(helper.get(suiteOpts.name, suiteOpts.loc), function (testSuite) {
+    if (_.contains(suiteOpts.ignoreSuites, testSuite.title)) return;
+
+    suite(suiteOpts.name + "/" + testSuite.title, function () {
+      _.each(testSuite.tests, function (task) {
+        if (_.contains(suiteOpts.ignoreTasks, task.title) || _.contains(suiteOpts.ignoreTasks, testSuite.title + "/" + task.title)) return;
+
+        var runTest = function (done) {
+          var runTask = function () {
+            try {
+              run(task, done);
+            } catch (err) {
+              if (task.options.after) task.options.after();
+              throw err;
+            }
+          };
+
+          _.extend(task.options, taskOpts);
+          if (dynamicOpts) dynamicOpts(task.options, task);
+
+          var throwMsg = task.options.throws;
+          if (throwMsg) {
+            // internal api doesn't have this option but it's best not to pollute
+            // the options object with useless options
+            delete task.options.throws;
+
+            assert.throws(runTask, function (err) {
+              return throwMsg === true || err.message.indexOf(throwMsg) >= 0;
+            });
+          } else {
+            runTask();
+          }
+        };
+
+        var callback;
+        if (task.options.asyncExec) {
+          callback = runTest;
+        } else {
+          callback = function () {
+            return runTest();
+          };
+        }
+
+        test(task.title, !task.disabled && callback);
+      });
+    });
+  });
+};
diff --git a/test/esnext.js b/test/esnext.js
new file mode 100644
index 0000000000..86558a55c6
--- /dev/null
+++ b/test/esnext.js
@@ -0,0 +1,5 @@
+if (!process.env.ALL_6TO5_TESTS) return;
+
+require("./_transformation-helper")({
+  name: "esnext"
+});
diff --git a/test/fixtures/esnext/es6-arrow-functions/arguments-refers-to-parent-function.js b/test/fixtures/esnext/es6-arrow-functions/arguments-refers-to-parent-function.js
new file mode 100644
index 0000000000..d299fb5379
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/arguments-refers-to-parent-function.js
@@ -0,0 +1,57 @@
+function makeMultiplier() {
+  // `arguments` should refer to `makeMultiplier`'s arguments.
+  return (n) => [].slice.call(arguments).reduce((a, b) => a * b) * n;
+}
+
+function toArray() {
+  // Intentionally nest arrow functions to ensure `arguments` is put inside
+  // `toArray`'s scope.
+  return (() => (arguments, (() => [].slice.call(arguments)).call())).call();
+}
+
+function returnDotArguments(object) {
+  // Ensure `arguments` is not treated as a reference to the magic value.
+  return (() => object.arguments).call();
+}
+
+function returnArgumentsObject() {
+  // Ensure `arguments` is not treated as a reference to the magic value.
+  return (() => ({arguments: 1})).call();
+}
+
+function makeArgumentsReturner() {
+  return (() => function() {
+    return [].slice.call(arguments);
+  }).call();
+}
+
+// i.e. 2 * 3 * 4 == 24, not 16 (4 * 4)
+assert.equal(
+  makeMultiplier(2, 3)(4),
+  24,
+  'ensure `arguments` is hoisted out to the first non-arrow scope'
+);
+
+assert.deepEqual(
+  toArray(1, 2, 3),
+  [1, 2, 3],
+  'ensure `arguments` is hoisted out to the first non-arrow scope'
+);
+
+assert.equal(
+  returnDotArguments({arguments: 1}),
+  1,
+  'member accesses with `arguments` property should not be replaced'
+);
+
+assert.deepEqual(
+  returnArgumentsObject(),
+  {arguments: 1},
+  'object property keys named `arguments` should not be replaced'
+);
+
+assert.deepEqual(
+  makeArgumentsReturner()(1, 2, 3),
+  [1, 2, 3],
+  'arguments should not be hoisted from inside non-arrow functions'
+);
diff --git a/test/fixtures/esnext/es6-arrow-functions/does-not-bind-this-from-standard-function.js b/test/fixtures/esnext/es6-arrow-functions/does-not-bind-this-from-standard-function.js
new file mode 100644
index 0000000000..6f3ffee93a
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/does-not-bind-this-from-standard-function.js
@@ -0,0 +1,5 @@
+var dynamicThisGetter = () => function () { return this; };
+assert.equal(
+  '(' + dynamicThisGetter.toString() + ')',
+  '(function () {\n  return function () {\n    return this;\n  };\n})'
+);
diff --git a/test/fixtures/esnext/es6-arrow-functions/empty-arrow-function.js b/test/fixtures/esnext/es6-arrow-functions/empty-arrow-function.js
new file mode 100644
index 0000000000..0b95435853
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/empty-arrow-function.js
@@ -0,0 +1,2 @@
+var empty = () => {};
+assert.equal(empty(), undefined);
diff --git a/test/fixtures/esnext/es6-arrow-functions/handles-nested-context-bindings.js b/test/fixtures/esnext/es6-arrow-functions/handles-nested-context-bindings.js
new file mode 100644
index 0000000000..03041f0297
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/handles-nested-context-bindings.js
@@ -0,0 +1,12 @@
+var obj = {
+  method: function() {
+    return () => (this, () => this);
+  },
+
+  method2: function() {
+    return () => () => this;
+  }
+};
+
+assert.strictEqual(obj.method()()(), obj);
+assert.strictEqual(obj.method2()()(), obj);
diff --git a/test/fixtures/esnext/es6-arrow-functions/no-parens-for-low-precedence-expression-body.js b/test/fixtures/esnext/es6-arrow-functions/no-parens-for-low-precedence-expression-body.js
new file mode 100644
index 0000000000..66fad996e5
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/no-parens-for-low-precedence-expression-body.js
@@ -0,0 +1,2 @@
+var square = x => x * x;
+assert.equal(square(4), 16);
diff --git a/test/fixtures/esnext/es6-arrow-functions/object-literal-needs-parens.js b/test/fixtures/esnext/es6-arrow-functions/object-literal-needs-parens.js
new file mode 100644
index 0000000000..3ec553b180
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/object-literal-needs-parens.js
@@ -0,0 +1,2 @@
+var keyMaker = val => ({ key: val });
+assert.deepEqual(keyMaker(9), { key: 9 });
diff --git a/test/fixtures/esnext/es6-arrow-functions/only-lexical-this-not-dynamic-this.js b/test/fixtures/esnext/es6-arrow-functions/only-lexical-this-not-dynamic-this.js
new file mode 100644
index 0000000000..68f68c14dc
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/only-lexical-this-not-dynamic-this.js
@@ -0,0 +1,7 @@
+var obj = {
+  method: function() {
+    return () => this;
+  }
+};
+
+assert.strictEqual(obj.method()(), obj);
diff --git a/test/fixtures/esnext/es6-arrow-functions/passed-to-function.js b/test/fixtures/esnext/es6-arrow-functions/passed-to-function.js
new file mode 100644
index 0000000000..75fbefbacd
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/passed-to-function.js
@@ -0,0 +1,2 @@
+var odds = [0, 2, 4].map(v => v + 1);
+assert.deepEqual(odds, [1, 3, 5]);
diff --git a/test/fixtures/esnext/es6-arrow-functions/single-param-does-not-need-parens.js b/test/fixtures/esnext/es6-arrow-functions/single-param-does-not-need-parens.js
new file mode 100644
index 0000000000..c2b56e7bbc
--- /dev/null
+++ b/test/fixtures/esnext/es6-arrow-functions/single-param-does-not-need-parens.js
@@ -0,0 +1,2 @@
+var identity = x => x;
+assert.equal(identity(1), 1);
diff --git a/test/fixtures/esnext/es6-classes/anonymous-class.js b/test/fixtures/esnext/es6-classes/anonymous-class.js
new file mode 100644
index 0000000000..231ba49b9e
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/anonymous-class.js
@@ -0,0 +1,29 @@
+var Animal = class {
+  sayHi() {
+    return 'Hi, I am a '+this.type()+'.';
+  }
+
+  static getName() {
+    return 'Animal';
+  }
+};
+
+var Dog = class extends Animal {
+  type() { return 'dog'; }
+
+  sayHi() {
+    return super() + ' WOOF!';
+  }
+
+  static getName() {
+    return super() + '/Dog';
+  }
+};
+
+assert.equal(new Dog().sayHi(), 'Hi, I am a dog. WOOF!');
+assert.equal(Dog.getName(), 'Animal/Dog');
+
+var count = 0;
+var Cat = class extends (function(){ count++; return Animal; })() {};
+
+assert.equal(count, 1);
diff --git a/test/fixtures/esnext/es6-classes/call-super-function.js b/test/fixtures/esnext/es6-classes/call-super-function.js
new file mode 100644
index 0000000000..5c7efe0dc6
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/call-super-function.js
@@ -0,0 +1,21 @@
+class Animal {
+  sayHi() {
+    return 'I am an animal.'
+  }
+
+  sayOther() {
+    return 'WAT?!';
+  }
+}
+
+class Horse extends Animal {
+  sayHi() {
+    return super.sayOther();
+  }
+
+  sayOther() {
+    return 'I see dead objects.';
+  }
+}
+
+assert.equal(new Horse().sayHi(), 'WAT?!');
diff --git a/test/fixtures/esnext/es6-classes/class-expressions.js b/test/fixtures/esnext/es6-classes/class-expressions.js
new file mode 100644
index 0000000000..1c2bb96a80
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/class-expressions.js
@@ -0,0 +1,9 @@
+var Person = (class Person {});
+assert.equal(typeof Person, 'function');
+
+assert.equal(
+  (function(){ return (class Person {}); })().name,
+  'Person'
+);
+
+assert.equal(typeof (class {}), 'function');
diff --git a/test/fixtures/esnext/es6-classes/class-extend.js b/test/fixtures/esnext/es6-classes/class-extend.js
new file mode 100644
index 0000000000..56035dd0b6
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/class-extend.js
@@ -0,0 +1,15 @@
+class Animal {
+  sayHi() {
+    return 'Hi, I am a '+this.type()+'.';
+  }
+}
+
+class Dog extends Animal {
+  type() { return 'dog'; }
+
+  sayHi() {
+    return super() + ' WOOF!';
+  }
+}
+
+assert.equal(new Dog().sayHi(), 'Hi, I am a dog. WOOF!');
diff --git a/test/fixtures/esnext/es6-classes/class-with-constructor.js b/test/fixtures/esnext/es6-classes/class-with-constructor.js
new file mode 100644
index 0000000000..4dcf3296f0
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/class-with-constructor.js
@@ -0,0 +1,14 @@
+class Multiplier {
+  constructor(n=1) {
+    this.n = n;
+  }
+
+  multiply(n=1) {
+    return n * this.n;
+  }
+}
+
+assert.equal(new Multiplier().n, 1);
+assert.equal(new Multiplier(6).n, 6);
+assert.equal(new Multiplier().multiply(), 1);
+assert.equal(new Multiplier(2).multiply(3), 6);
diff --git a/test/fixtures/esnext/es6-classes/class-with-method-declaration.js b/test/fixtures/esnext/es6-classes/class-with-method-declaration.js
new file mode 100644
index 0000000000..f8d9d7a207
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/class-with-method-declaration.js
@@ -0,0 +1,10 @@
+class Person {
+  getName() {
+    return this.firstName + ' ' + this.lastName;
+  }
+}
+
+var me = new Person();
+me.firstName = 'Brian';
+me.lastName = 'Donovan';
+assert.equal(me.getName(), 'Brian Donovan');
diff --git a/test/fixtures/esnext/es6-classes/empty-named-class.js b/test/fixtures/esnext/es6-classes/empty-named-class.js
new file mode 100644
index 0000000000..602a6702d3
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/empty-named-class.js
@@ -0,0 +1,5 @@
+class Foo {
+}
+
+assert.equal(new Foo().constructor, Foo, 'Foo instances should have Foo as constructor');
+assert.ok(new Foo() instanceof Foo, 'Foo instances should be `instanceof` Foo');
diff --git a/test/fixtures/esnext/es6-classes/enumerable.js b/test/fixtures/esnext/es6-classes/enumerable.js
new file mode 100644
index 0000000000..392fda2ca9
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/enumerable.js
@@ -0,0 +1,20 @@
+class Point {
+  constructor(x, y) {
+    this.x = x;
+    this.y = y;
+  }
+
+  toString() {
+    return '(' + this.x + ', ' + this.y + ')';
+  }
+}
+
+var point = new Point(1, 2);
+var keys = [];
+
+for (var key in point) {
+  keys.push(key);
+}
+
+assert.equal(point.toString(), '(1, 2)');
+assert.deepEqual(keys.sort(), ['toString', 'x', 'y']);
diff --git a/test/fixtures/esnext/es6-classes/explicit-super-in-constructor.js b/test/fixtures/esnext/es6-classes/explicit-super-in-constructor.js
new file mode 100644
index 0000000000..d30f21cba5
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/explicit-super-in-constructor.js
@@ -0,0 +1,15 @@
+class Point {
+  constructor(x, y) {
+    this.x = x;
+    this.y = y;
+  }
+}
+
+class ZeroPoint extends Point {
+  constructor() {
+    super(0, 0);
+  }
+}
+
+assert.equal(new ZeroPoint().x, 0);
+assert.equal(new ZeroPoint().y, 0);
diff --git a/test/fixtures/esnext/es6-classes/extends-null.js b/test/fixtures/esnext/es6-classes/extends-null.js
new file mode 100644
index 0000000000..fa3821d8c7
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/extends-null.js
@@ -0,0 +1,4 @@
+class Obj extends null {}
+
+assert.strictEqual(Obj.toString, Function.toString);
+assert.strictEqual(new Obj().toString, undefined);
diff --git a/test/fixtures/esnext/es6-classes/getter-setter-super.js b/test/fixtures/esnext/es6-classes/getter-setter-super.js
new file mode 100644
index 0000000000..98d7bc0eea
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/getter-setter-super.js
@@ -0,0 +1,15 @@
+class Animal {
+  get sound() {
+    return 'I am a ' + this.type + '.';
+  }
+}
+
+class Cat extends Animal {
+  get type() { return 'cat'; }
+
+  get sound() {
+    return super.sound + ' MEOW!';
+  }
+}
+
+assert.equal(new Cat().sound, 'I am a cat. MEOW!');
diff --git a/test/fixtures/esnext/es6-classes/getter-setter.js b/test/fixtures/esnext/es6-classes/getter-setter.js
new file mode 100644
index 0000000000..8f9519f9ba
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/getter-setter.js
@@ -0,0 +1,28 @@
+class Person {
+  constructor(firstName, lastName) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
+  get name() {
+    return this.firstName + ' ' + this.lastName;
+  }
+
+  set name(name) {
+    var parts = name.split(' ');
+    this.firstName = parts[0];
+    this.lastName = parts[1];
+  }
+}
+
+var mazer = new Person('Mazer', 'Rackham');
+assert.equal(mazer.name, 'Mazer Rackham');
+mazer.name = 'Ender Wiggin';
+assert.equal(mazer.firstName, 'Ender');
+assert.equal(mazer.lastName, 'Wiggin');
+
+var forLoopProperties = [];
+for (var key in mazer) {
+  forLoopProperties.push(key);
+}
+assert.ok(forLoopProperties.indexOf('name') >= 0, 'getters/setters are enumerable');
diff --git a/test/fixtures/esnext/es6-classes/implicit-superclass.js b/test/fixtures/esnext/es6-classes/implicit-superclass.js
new file mode 100644
index 0000000000..96755df101
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/implicit-superclass.js
@@ -0,0 +1,9 @@
+class Obj {
+  constructor() {
+    super();
+  }
+}
+
+assert.doesNotThrow(function() {
+  new Obj();
+});
diff --git a/test/fixtures/esnext/es6-classes/method-declaration-with-arguments.js b/test/fixtures/esnext/es6-classes/method-declaration-with-arguments.js
new file mode 100644
index 0000000000..b70c56e68c
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/method-declaration-with-arguments.js
@@ -0,0 +1,7 @@
+class Tripler {
+  triple(n) {
+    return n * 3;
+  }
+}
+
+assert.equal(new Tripler().triple(2), 6);
diff --git a/test/fixtures/esnext/es6-classes/methods-are-writable.js b/test/fixtures/esnext/es6-classes/methods-are-writable.js
new file mode 100644
index 0000000000..19ffd5aa73
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/methods-are-writable.js
@@ -0,0 +1,12 @@
+var value;
+
+class Foo {
+  foo() {
+    value = 1;
+  }
+}
+
+var foo = new Foo();
+foo.foo = function() { value = 2; };
+foo.foo();
+assert.equal(value, 2);
diff --git a/test/fixtures/esnext/es6-classes/methods-with-rest-params.js b/test/fixtures/esnext/es6-classes/methods-with-rest-params.js
new file mode 100644
index 0000000000..77b7bb0774
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/methods-with-rest-params.js
@@ -0,0 +1,28 @@
+class Joiner {
+  constructor(string) {
+    this.string = string;
+  }
+
+  join(...items) {
+    return items.join(this.string);
+  }
+
+  static join(string, ...items) {
+    var joiner = new this(string);
+    // TODO: use spread params here
+    return joiner.join.apply(joiner, items);
+  }
+}
+
+class ArrayLike {
+  constructor(...items) {
+    items.forEach(function(item, i) {
+      this[i] = item;
+    }.bind(this));
+    this.length = items.length;
+  }
+}
+
+var joiner = new Joiner(' & ');
+assert.equal(joiner.join(4, 5, 6), '4 & 5 & 6');
+assert.equal(new ArrayLike('a', 'b')[1], 'b');
diff --git a/test/fixtures/esnext/es6-classes/static-getter.js b/test/fixtures/esnext/es6-classes/static-getter.js
new file mode 100644
index 0000000000..af9fe0afe6
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/static-getter.js
@@ -0,0 +1,12 @@
+class Point {
+  constructor(x, y) {
+    this.x = x;
+    this.y = y;
+  }
+
+  static get ORIGIN() {
+    return new this(0, 0);
+  }
+}
+
+assert.deepEqual(Point.ORIGIN, new Point(0, 0));
\ No newline at end of file
diff --git a/test/fixtures/esnext/es6-classes/static-method.js b/test/fixtures/esnext/es6-classes/static-method.js
new file mode 100644
index 0000000000..564fb13c5b
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/static-method.js
@@ -0,0 +1,30 @@
+class Tripler {
+  static triple(n=1) {
+    return n * 3;
+  }
+
+  static toString() {
+    return '3' + super() + '3';
+  }
+}
+
+class MegaTripler extends Tripler {
+  static triple(n=1) {
+    return super(n) * super(n);
+  }
+}
+
+var tripler = new Tripler();
+
+assert.equal(Tripler.triple(), 3);
+assert.equal(Tripler.triple(2), 6);
+assert.equal(tripler.triple, undefined);
+
+assert.equal(Tripler.toString(), '3' + Object.toString.call(Tripler) + '3');
+
+var mega = new MegaTripler();
+
+assert.equal(MegaTripler.triple(2), 36);
+assert.equal(mega.triple, undefined);
+
+assert.equal(MegaTripler.toString(), '3' + Object.toString.call(MegaTripler) + '3');
diff --git a/test/fixtures/esnext/es6-classes/static-setter.js b/test/fixtures/esnext/es6-classes/static-setter.js
new file mode 100644
index 0000000000..08fae30af5
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/static-setter.js
@@ -0,0 +1,7 @@
+class Person {
+  static set DB(value) {
+    assert.equal(value, 'mysql');
+  }
+}
+
+Person.DB = 'mysql';
diff --git a/test/fixtures/esnext/es6-classes/super-change-proto.js b/test/fixtures/esnext/es6-classes/super-change-proto.js
new file mode 100644
index 0000000000..f7c653b460
--- /dev/null
+++ b/test/fixtures/esnext/es6-classes/super-change-proto.js
@@ -0,0 +1,21 @@
+var log = '';
+
+class Base {
+  p() { log += '[Base]'; }
+}
+
+class OtherBase {
+  p() { log += '[OtherBase]'; }
+}
+
+class Derived extends Base {
+  p() {
+    log += '[Derived]';
+    super();
+    Derived.prototype.__proto__ = OtherBase.prototype;
+    super();
+  }
+}
+
+new Derived().p();
+assert.equal(log, '[Derived][Base][OtherBase]');
diff --git a/test/fixtures/esnext/es6-computed-properties/accessor.js b/test/fixtures/esnext/es6-computed-properties/accessor.js
new file mode 100644
index 0000000000..bedcb7785a
--- /dev/null
+++ b/test/fixtures/esnext/es6-computed-properties/accessor.js
@@ -0,0 +1,8 @@
+var x = 'y';
+
+var foo = {
+  get [x]() { return this._y; },
+  set [x](v) { this._y = v; }
+};
+
+assert.equal((foo.y = 10, foo.y), 10);
diff --git a/test/fixtures/esnext/es6-computed-properties/method.js b/test/fixtures/esnext/es6-computed-properties/method.js
new file mode 100644
index 0000000000..e28e4d18d5
--- /dev/null
+++ b/test/fixtures/esnext/es6-computed-properties/method.js
@@ -0,0 +1,3 @@
+var x = 'y';
+assert.equal({[x]: function() { return 10; }}.y(), 10);
+assert.equal({[x + 'y']() { return 10; }}.yy(), 10);
diff --git a/test/fixtures/esnext/es6-computed-properties/nested.js b/test/fixtures/esnext/es6-computed-properties/nested.js
new file mode 100644
index 0000000000..ea11b2c6f6
--- /dev/null
+++ b/test/fixtures/esnext/es6-computed-properties/nested.js
@@ -0,0 +1,4 @@
+var x = 'y';
+var foo = {[x]: 10, z: {[x]: 10}};
+assert.equal(foo.y + foo.z.y, 20);
+assert.equal({[x]: {[x]: {[x]: 10}}}.y.y.y, 10);
diff --git a/test/fixtures/esnext/es6-computed-properties/simple.js b/test/fixtures/esnext/es6-computed-properties/simple.js
new file mode 100644
index 0000000000..21e56afe58
--- /dev/null
+++ b/test/fixtures/esnext/es6-computed-properties/simple.js
@@ -0,0 +1,3 @@
+var x = 'y';
+assert.equal({[x]: 10}.y, 10);
+assert.equal({[x + 'y']: 10}.yy, 10);
diff --git a/test/fixtures/esnext/es6-default-parameters/arity.js b/test/fixtures/esnext/es6-default-parameters/arity.js
new file mode 100644
index 0000000000..030f3e08ea
--- /dev/null
+++ b/test/fixtures/esnext/es6-default-parameters/arity.js
@@ -0,0 +1,3 @@
+assert.equal((function(a){}).length, 1);
+assert.equal((function(a=5){}).length, 0);
+assert.equal((function(a, b, c=5){}).length, 2);
diff --git a/test/fixtures/esnext/es6-default-parameters/arrow-function.js b/test/fixtures/esnext/es6-default-parameters/arrow-function.js
new file mode 100644
index 0000000000..66c0068d94
--- /dev/null
+++ b/test/fixtures/esnext/es6-default-parameters/arrow-function.js
@@ -0,0 +1,8 @@
+function makeMultiplier(x=1) {
+  return (y=1) => x * y;
+}
+
+assert.equal(makeMultiplier()(), 1);
+assert.equal(makeMultiplier(2)(3), 6);
+assert.deepEqual([1, 2, 3].map(makeMultiplier(2)), [2, 4, 6]);
+assert.deepEqual([undefined, null, 0].map(makeMultiplier(2)), [2, 0, 0]);
diff --git a/test/fixtures/esnext/es6-default-parameters/null-vs-undefined.js b/test/fixtures/esnext/es6-default-parameters/null-vs-undefined.js
new file mode 100644
index 0000000000..b028ba3e09
--- /dev/null
+++ b/test/fixtures/esnext/es6-default-parameters/null-vs-undefined.js
@@ -0,0 +1,5 @@
+function foo(x=5, y=6) {
+  return [x, y];
+}
+
+assert.deepEqual(foo(undefined, null), [5, null]);
diff --git a/test/fixtures/esnext/es6-default-parameters/scope.js b/test/fixtures/esnext/es6-default-parameters/scope.js
new file mode 100644
index 0000000000..54848cd8f2
--- /dev/null
+++ b/test/fixtures/esnext/es6-default-parameters/scope.js
@@ -0,0 +1,11 @@
+function call(fn, context=this) {
+  return fn.call(context);
+}
+
+var context = {a: 99};
+
+// use the default parameter
+assert.strictEqual(call.call(context, function(){ return this.a; }), 99);
+
+// explicitly provide the default parameter value
+assert.strictEqual(call(function(){ return this.a; }, context), 99);
diff --git a/test/fixtures/esnext/es6-default-parameters/simple-function.js b/test/fixtures/esnext/es6-default-parameters/simple-function.js
new file mode 100644
index 0000000000..d7bf1bfa1c
--- /dev/null
+++ b/test/fixtures/esnext/es6-default-parameters/simple-function.js
@@ -0,0 +1,4 @@
+function foo(x=5) {
+  return x;
+}
+assert.equal(foo(), 5);
diff --git a/test/fixtures/esnext/es6-object-concise/method-arguments.js b/test/fixtures/esnext/es6-object-concise/method-arguments.js
new file mode 100644
index 0000000000..392586fc9b
--- /dev/null
+++ b/test/fixtures/esnext/es6-object-concise/method-arguments.js
@@ -0,0 +1,7 @@
+var a = {
+  echo(c) {
+    return c;
+  }
+};
+
+assert.strictEqual(a.echo(1), 1);
diff --git a/test/fixtures/esnext/es6-object-concise/method-context.js b/test/fixtures/esnext/es6-object-concise/method-context.js
new file mode 100644
index 0000000000..53c4bf3bc7
--- /dev/null
+++ b/test/fixtures/esnext/es6-object-concise/method-context.js
@@ -0,0 +1,9 @@
+var a = {
+  b() {
+    return this;
+  }
+};
+
+var context = {};
+assert.strictEqual(a.b(), a);
+assert.strictEqual(a.b.call(context), context);
\ No newline at end of file
diff --git a/test/fixtures/esnext/es6-object-concise/method-has-name.js b/test/fixtures/esnext/es6-object-concise/method-has-name.js
new file mode 100644
index 0000000000..320ec33b54
--- /dev/null
+++ b/test/fixtures/esnext/es6-object-concise/method-has-name.js
@@ -0,0 +1,7 @@
+var a = {
+  b() {
+    return 'c';
+  }
+};
+
+assert.equal(a.b.name, 'b');
diff --git a/test/fixtures/esnext/es6-object-concise/method-is-not-in-scope-inside.js b/test/fixtures/esnext/es6-object-concise/method-is-not-in-scope-inside.js
new file mode 100644
index 0000000000..4f58980df0
--- /dev/null
+++ b/test/fixtures/esnext/es6-object-concise/method-is-not-in-scope-inside.js
@@ -0,0 +1,9 @@
+var b = 1;
+
+var a = {
+  b() {
+    return b;
+  }
+};
+
+assert.equal(a.b(), 1);
diff --git a/test/fixtures/esnext/es6-object-concise/method-to-string.js b/test/fixtures/esnext/es6-object-concise/method-to-string.js
new file mode 100644
index 0000000000..ba3f86cb78
--- /dev/null
+++ b/test/fixtures/esnext/es6-object-concise/method-to-string.js
@@ -0,0 +1,10 @@
+var a = {
+  b() {
+    return b;
+  }
+};
+
+assert.ok(
+  /return b/.test(a.b.toString()),
+  'toString contains body'
+);
\ No newline at end of file
diff --git a/test/fixtures/esnext/es6-object-concise/method.js b/test/fixtures/esnext/es6-object-concise/method.js
new file mode 100644
index 0000000000..1707a7aebb
--- /dev/null
+++ b/test/fixtures/esnext/es6-object-concise/method.js
@@ -0,0 +1,7 @@
+var a = {
+  b() {
+    return 'c';
+  }
+};
+
+assert.equal(a.b(), 'c');
diff --git a/test/fixtures/esnext/es6-rest-parameters/arrow-fn.js b/test/fixtures/esnext/es6-rest-parameters/arrow-fn.js
new file mode 100644
index 0000000000..eb9d8ea8c5
--- /dev/null
+++ b/test/fixtures/esnext/es6-rest-parameters/arrow-fn.js
@@ -0,0 +1,5 @@
+var join = (joinStr, ...items) => {
+  return items.join(joinStr);
+};
+
+assert.deepEqual(join(' ', 'a', 'b', 'c'), 'a b c');
diff --git a/test/fixtures/esnext/es6-rest-parameters/declaration.js b/test/fixtures/esnext/es6-rest-parameters/declaration.js
new file mode 100644
index 0000000000..2d3ca5d283
--- /dev/null
+++ b/test/fixtures/esnext/es6-rest-parameters/declaration.js
@@ -0,0 +1,5 @@
+function join(joinStr, ...items) {
+  return items.join(joinStr);
+}
+
+assert.deepEqual(join(' ', 'a', 'b', 'c'), 'a b c');
diff --git a/test/fixtures/esnext/es6-rest-parameters/rest.js b/test/fixtures/esnext/es6-rest-parameters/rest.js
new file mode 100644
index 0000000000..769bf2d2a4
--- /dev/null
+++ b/test/fixtures/esnext/es6-rest-parameters/rest.js
@@ -0,0 +1,5 @@
+var join = function(joinStr, ...items) {
+  return items.join(joinStr);
+};
+
+assert.deepEqual(join(' ', 'a', 'b', 'c'), 'a b c');
diff --git a/test/fixtures/esnext/es6-spread/arguments-as-array.js b/test/fixtures/esnext/es6-spread/arguments-as-array.js
new file mode 100644
index 0000000000..d0957e35b4
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/arguments-as-array.js
@@ -0,0 +1,6 @@
+function arrayOf() {
+  return [...arguments];
+}
+
+assert.equal(Object.prototype.toString.call(arrayOf()), '[object Array]');
+assert.deepEqual(arrayOf(1, 2, 3), [1, 2, 3]);
diff --git a/test/fixtures/esnext/es6-spread/array-literal.js b/test/fixtures/esnext/es6-spread/array-literal.js
new file mode 100644
index 0000000000..3c1bea826f
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/array-literal.js
@@ -0,0 +1,3 @@
+var names = ['Brian', 'Madeline'];
+assert.deepEqual(['Thomas', ...names], ['Thomas', 'Brian', 'Madeline']);
+assert.deepEqual([1, 2, ...[3, 4, 5]], [1, 2, 3, 4, 5]);
diff --git a/test/fixtures/esnext/es6-spread/call-with-array-literal.js b/test/fixtures/esnext/es6-spread/call-with-array-literal.js
new file mode 100644
index 0000000000..19cffabc6d
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/call-with-array-literal.js
@@ -0,0 +1,5 @@
+function sum(...numbers) {
+  return numbers.reduce(function(sum, n) { return n + sum; }, 0);
+}
+
+assert.equal(sum(4, 5, ...[10, 20, 30]), 69);
diff --git a/test/fixtures/esnext/es6-spread/inside-function-expression.js b/test/fixtures/esnext/es6-spread/inside-function-expression.js
new file mode 100644
index 0000000000..c2c06da399
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/inside-function-expression.js
@@ -0,0 +1,10 @@
+var object = {
+  list: [],
+
+  append: function(...items) {
+    this.list.push(...items);
+  }
+};
+
+object.append(1, 2, ...[3, 4]);
+assert.deepEqual(object.list, [1, 2, 3, 4]);
diff --git a/test/fixtures/esnext/es6-spread/iterator.js b/test/fixtures/esnext/es6-spread/iterator.js
new file mode 100644
index 0000000000..6e5ef15ba2
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/iterator.js
@@ -0,0 +1,16 @@
+var obj = {
+  [Symbol.iterator]: function() {
+    var ttl = 3;
+    return {
+      next: function() {
+        if (ttl === 0) {
+          return { done: true, value: null };
+        } else {
+          return { done: false, value: ttl-- };
+        }
+      }
+    };
+  }
+};
+
+assert.deepEqual([3, 2, 1], [...obj]);
diff --git a/test/fixtures/esnext/es6-spread/new-object.js b/test/fixtures/esnext/es6-spread/new-object.js
new file mode 100644
index 0000000000..6e4af74279
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/new-object.js
@@ -0,0 +1,11 @@
+var callCount = 0;
+function getArray() {
+  callCount++;
+  return Array;
+}
+
+assert.deepEqual([1, 2, 3], new Array(...[1, 2, 3]));
+
+// Ensure the expression of the function being initialized is not copied.
+assert.deepEqual([1, 2, 3], new (getArray())(...[1, 2, 3]));
+assert.equal(callCount, 1);
diff --git a/test/fixtures/esnext/es6-spread/preserve-context.js b/test/fixtures/esnext/es6-spread/preserve-context.js
new file mode 100644
index 0000000000..e63f88e788
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/preserve-context.js
@@ -0,0 +1,35 @@
+var MATH = {
+  sum: function(...numbers) {
+    return numbers.reduce(this.add, 0);
+  },
+
+  add: function(a, b) {
+    return a + b;
+  }
+};
+
+assert.equal(MATH.sum(1, ...[2, 3]), 6);
+
+// Ensure that the below does not expand to this:
+//
+//   obj.getSelf().call.apply(obj.getSelf(), []);
+//
+
+var ops = [];
+var obj = {
+  getSelf: function() {
+    ops.push('getSelf');
+    return this;
+  },
+
+  doCall: function() {
+    ops.push('doCall', this);
+  }
+};
+
+obj.getSelf().doCall(...[]);
+assert.deepEqual(ops, ['getSelf', 'doCall', obj]);
+
+ops = [];
+obj['getSelf']().doCall(...[]);
+assert.deepEqual(ops, ['getSelf', 'doCall', obj]);
diff --git a/test/fixtures/esnext/es6-spread/simple-function-call.js b/test/fixtures/esnext/es6-spread/simple-function-call.js
new file mode 100644
index 0000000000..106bfa55be
--- /dev/null
+++ b/test/fixtures/esnext/es6-spread/simple-function-call.js
@@ -0,0 +1,6 @@
+function sum(...numbers) {
+  return numbers.reduce(function(sum, n) { return n + sum; }, 0);
+}
+
+var numbers = [1, 2, 3];
+assert.equal(sum(...numbers), 6);
diff --git a/test/fixtures/esnext/es6-templates/multi-line.js b/test/fixtures/esnext/es6-templates/multi-line.js
new file mode 100644
index 0000000000..6d1be1c2bc
--- /dev/null
+++ b/test/fixtures/esnext/es6-templates/multi-line.js
@@ -0,0 +1,4 @@
+var s = `a
+    b
+    c`;
+assert.equal(s, 'a\n    b\n    c');
diff --git a/test/fixtures/esnext/es6-templates/nested-interpolation.js b/test/fixtures/esnext/es6-templates/nested-interpolation.js
new file mode 100644
index 0000000000..83083e9fd0
--- /dev/null
+++ b/test/fixtures/esnext/es6-templates/nested-interpolation.js
@@ -0,0 +1,4 @@
+assert.strictEqual(
+  `a${1}b${`${1+1}c`}3`,
+  'a1b2c3'
+);
diff --git a/test/fixtures/esnext/es6-templates/no-interpolation.js b/test/fixtures/esnext/es6-templates/no-interpolation.js
new file mode 100644
index 0000000000..1854b04ff5
--- /dev/null
+++ b/test/fixtures/esnext/es6-templates/no-interpolation.js
@@ -0,0 +1,2 @@
+var s = `str`;
+assert.equal(s, 'str');
diff --git a/test/fixtures/esnext/es6-templates/raw-tagged-template-expression.js b/test/fixtures/esnext/es6-templates/raw-tagged-template-expression.js
new file mode 100644
index 0000000000..831ad050ab
--- /dev/null
+++ b/test/fixtures/esnext/es6-templates/raw-tagged-template-expression.js
@@ -0,0 +1,6 @@
+function r(strings) {
+  assert.equal(strings.raw[0], '\\n');
+  return strings.raw.join('');
+}
+
+assert.equal(r `\n`, '\\n');
diff --git a/test/fixtures/esnext/es6-templates/simple-interpolation.js b/test/fixtures/esnext/es6-templates/simple-interpolation.js
new file mode 100644
index 0000000000..b96a02a543
--- /dev/null
+++ b/test/fixtures/esnext/es6-templates/simple-interpolation.js
@@ -0,0 +1,2 @@
+var s = `1 + 1 = ${1 + 1}`;
+assert.equal(s, '1 + 1 = 2');
diff --git a/test/fixtures/esnext/es6-templates/tagged-template-expression.js b/test/fixtures/esnext/es6-templates/tagged-template-expression.js
new file mode 100644
index 0000000000..5b894c55ac
--- /dev/null
+++ b/test/fixtures/esnext/es6-templates/tagged-template-expression.js
@@ -0,0 +1,26 @@
+function tag(strings) {
+  var values = [].slice.call(arguments, 1);
+  assert.equal(strings[0], 'a');
+  assert.equal(strings[1], 'b');
+  assert.equal(values[0], 42);
+  return 'whatever';
+}
+assert.equal(tag `a${ 42 }b`, 'whatever');
+
+function tagInterpolateFirst(strings) {
+  var values = [].slice.call(arguments, 1);
+  assert.equal(strings[0], '');
+  assert.equal(strings[1], 'b');
+  assert.equal(values[0], 42);
+  return 'whatever';
+}
+assert.equal(tagInterpolateFirst `${ 42 }b`, 'whatever');
+
+function tagInterpolateLast(strings) {
+  var values = [].slice.call(arguments, 1);
+  assert.equal(strings[0], 'a');
+  assert.equal(strings[1], '');
+  assert.equal(values[0], 42);
+  return 'whatever';
+}
+assert.equal(tagInterpolateLast `a${ 42 }`, 'whatever');
diff --git a/test/fixtures/transformation/api/options.json b/test/fixtures/transformation/api/options.json
new file mode 100644
index 0000000000..df1ae3d305
--- /dev/null
+++ b/test/fixtures/transformation/api/options.json
@@ -0,0 +1,3 @@
+{
+  "noCheckAst": true
+}
diff --git a/test/fixtures/transformation/es6-arrow-functions/default-parameters/expected.js b/test/fixtures/transformation/es6-arrow-functions/default-parameters/expected.js
index baba36b081..19d93a94d6 100644
--- a/test/fixtures/transformation/es6-arrow-functions/default-parameters/expected.js
+++ b/test/fixtures/transformation/es6-arrow-functions/default-parameters/expected.js
@@ -1,7 +1,7 @@
 "use strict";
 
-var some = function (count) {
-  if (count === undefined) count = "30";
+var some = function () {
+  var count = arguments[0] === undefined ? "30" : arguments[0];
   console.log("count", count);
 };
 
diff --git a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
index 1eec391c5e..1600d655fb 100644
--- a/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes/accessing-super-class/expected.js
@@ -2,6 +2,9 @@
 
 var _slice = Array.prototype.slice;
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
@@ -22,8 +25,8 @@ var Test = (function () {
     _Foo.prototype.test.call(this);
     foob(_Foo);
 
-    _Foo.call.apply(null, [this].concat(_slice.call(arguments)));
-    _Foo.call.apply(null, [this, "test"].concat(_slice.call(arguments)));
+    _Foo.call.apply(_Foo, [this].concat(_slice.call(arguments)));
+    _Foo.call.apply(_Foo, [this, "test"].concat(_slice.call(arguments)));
 
     (_Foo$prototype$test = _Foo.prototype.test).call.apply(_Foo$prototype$test, [this].concat(_slice.call(arguments)));
     (_Foo$prototype$test2 = _Foo.prototype.test).call.apply(_Foo$prototype$test2, [this, "test"].concat(_slice.call(arguments)));
diff --git a/test/fixtures/transformation/es6-classes/accessing-super-properties/expected.js b/test/fixtures/transformation/es6-classes/accessing-super-properties/expected.js
index 95ba3c53f4..29526be129 100644
--- a/test/fixtures/transformation/es6-classes/accessing-super-properties/expected.js
+++ b/test/fixtures/transformation/es6-classes/accessing-super-properties/expected.js
@@ -1,6 +1,9 @@
 "use strict";
 
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
diff --git a/test/fixtures/transformation/es6-classes/calling-super-properties/expected.js b/test/fixtures/transformation/es6-classes/calling-super-properties/expected.js
index 1b2b38ce31..7e8f2bfd43 100644
--- a/test/fixtures/transformation/es6-classes/calling-super-properties/expected.js
+++ b/test/fixtures/transformation/es6-classes/calling-super-properties/expected.js
@@ -1,6 +1,9 @@
 "use strict";
 
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
diff --git a/test/fixtures/transformation/es6-classes/constructor/expected.js b/test/fixtures/transformation/es6-classes/constructor/expected.js
index d43c12f6e7..cc5264d5b6 100644
--- a/test/fixtures/transformation/es6-classes/constructor/expected.js
+++ b/test/fixtures/transformation/es6-classes/constructor/expected.js
@@ -1,6 +1,9 @@
 "use strict";
 
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
diff --git a/test/fixtures/transformation/es6-classes/super-class-id-member-expression/expected.js b/test/fixtures/transformation/es6-classes/super-class-id-member-expression/expected.js
index 3e58ae4cf4..d9a40e4753 100644
--- a/test/fixtures/transformation/es6-classes/super-class-id-member-expression/expected.js
+++ b/test/fixtures/transformation/es6-classes/super-class-id-member-expression/expected.js
@@ -1,6 +1,9 @@
 "use strict";
 
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
@@ -15,7 +18,7 @@ var _inherits = function (child, parent) {
 var BaseController = (function () {
   var _Chaplin$Controller = Chaplin.Controller;
   var BaseController = function BaseController() {
-    if (_Chaplin$Controller) {
+    if (_Chaplin$Controller !== null) {
       _Chaplin$Controller.apply(this, arguments);
     }
   };
@@ -28,7 +31,7 @@ var BaseController = (function () {
 var BaseController2 = (function () {
   var _Chaplin$Controller$Another = Chaplin.Controller.Another;
   var BaseController2 = function BaseController2() {
-    if (_Chaplin$Controller$Another) {
+    if (_Chaplin$Controller$Another !== null) {
       _Chaplin$Controller$Another.apply(this, arguments);
     }
   };
diff --git a/test/fixtures/transformation/es6-classes/super-class/expected.js b/test/fixtures/transformation/es6-classes/super-class/expected.js
index d57ed0b72c..01534a385f 100644
--- a/test/fixtures/transformation/es6-classes/super-class/expected.js
+++ b/test/fixtures/transformation/es6-classes/super-class/expected.js
@@ -1,6 +1,9 @@
 "use strict";
 
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
@@ -15,7 +18,7 @@ var _inherits = function (child, parent) {
 var Test = (function () {
   var _Foo = Foo;
   var Test = function Test() {
-    if (_Foo) {
+    if (_Foo !== null) {
       _Foo.apply(this, arguments);
     }
   };
diff --git a/test/fixtures/transformation/es6-default-parameters/multiple/expected.js b/test/fixtures/transformation/es6-default-parameters/multiple/expected.js
index 55bc52c5c9..af684c28f7 100644
--- a/test/fixtures/transformation/es6-default-parameters/multiple/expected.js
+++ b/test/fixtures/transformation/es6-default-parameters/multiple/expected.js
@@ -1,12 +1,12 @@
 "use strict";
 
-var t = function (t, f) {
-  if (t === undefined) t = "foo";
-  if (f === undefined) f = 5;
+var t = function () {
+  var t = arguments[0] === undefined ? "foo" : arguments[0];
+  var f = arguments[1] === undefined ? 5 : arguments[1];
   return t + " bar " + f;
 };
 
-var a = function (t, f) {
-  if (f === undefined) f = 5;
+var a = function (t) {
+  var f = arguments[1] === undefined ? 5 : arguments[1];
   return t + " bar " + f;
 };
diff --git a/test/fixtures/transformation/es6-default-parameters/single/expected.js b/test/fixtures/transformation/es6-default-parameters/single/expected.js
index 5021d6e0ab..f953c7a0a9 100644
--- a/test/fixtures/transformation/es6-default-parameters/single/expected.js
+++ b/test/fixtures/transformation/es6-default-parameters/single/expected.js
@@ -1,6 +1,6 @@
 "use strict";
 
-var t = function (t) {
-  if (t === undefined) t = "foo";
+var t = function () {
+  var t = arguments[0] === undefined ? "foo" : arguments[0];
   return t + " bar";
 };
diff --git a/test/fixtures/transformation/es6-generators/LICENSE b/test/fixtures/transformation/es6-generators/LICENSE
deleted file mode 100644
index eba1d817f5..0000000000
--- a/test/fixtures/transformation/es6-generators/LICENSE
+++ /dev/null
@@ -1,7 +0,0 @@
-Copyright (c) 2014, Facebook, Inc.
-All rights reserved.
-
-This source code is licensed under the BSD-style license found in the
-https://raw.github.com/facebook/regenerator/master/LICENSE file. An
-additional grant of patent rights can be found in the PATENTS file in
-the same directory.
diff --git a/test/fixtures/transformation/es6-generators/block-binding-should-translate-block-binding-correctly/exec.js b/test/fixtures/transformation/es6-generators/block-binding-should-translate-block-binding-correctly/exec.js
deleted file mode 100644
index 140f327a37..0000000000
--- a/test/fixtures/transformation/es6-generators/block-binding-should-translate-block-binding-correctly/exec.js
+++ /dev/null
@@ -1,24 +0,0 @@
-function *gen() {
-  var a$0 = 0, a$1 = 1;
-
-  let a = 3;
-
-  {
-    let a = 1;
-    yield a + a$0;
-  }
-
-  {
-    let a = 2;
-    yield a - 1 + a$1;
-  }
-
-  yield a;
-}
-
-var g = gen();
-
-assert.deepEqual(g.next(), { value: 1, done: false });
-assert.deepEqual(g.next(), { value: 2, done: false });
-assert.deepEqual(g.next(), { value: 3, done: false });
-assert.deepEqual(g.next(), { value: void 0, done: true });
diff --git a/test/fixtures/transformation/es6-generators/block-binding-should-translate-block-binding-with-iife-correctly/exec.js b/test/fixtures/transformation/es6-generators/block-binding-should-translate-block-binding-with-iife-correctly/exec.js
deleted file mode 100644
index 3edc3451b3..0000000000
--- a/test/fixtures/transformation/es6-generators/block-binding-should-translate-block-binding-with-iife-correctly/exec.js
+++ /dev/null
@@ -1,22 +0,0 @@
-function *gen() {
-  let arr = [];
-
-  for (let x = 0; x < 3; x++) {
-    let y = x;
-    arr.push(function() { return y; });
-  }
-
-  {
-    let x;
-    while( x = arr.pop() ) {
-      yield x;
-    }
-  }
-}
-
-var g = gen();
-
-assert.equal(g.next().value(), 2);
-assert.equal(g.next().value(), 1);
-assert.equal(g.next().value(), 0);
-assert.deepEqual(g.next(), { value: void 0, done: true });
diff --git a/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-allow-nested-catch-parameters-of-the-same-name/exec.js b/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-allow-nested-catch-parameters-of-the-same-name/exec.js
deleted file mode 100644
index bfa31390c1..0000000000
--- a/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-allow-nested-catch-parameters-of-the-same-name/exec.js
+++ /dev/null
@@ -1,15 +0,0 @@
-function *gen() {
-  try {
-    genHelpers.raise("e1");
-  } catch (e) {
-    yield e;
-    try {
-      genHelpers.raise("e2");
-    } catch (e) {
-      yield e;
-    }
-    yield e;
-  }
-}
-
-genHelpers.check(gen(), ["e1", "e2", "e1"]);
diff --git a/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-leave-outer-variables-unmodified/exec.js b/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-leave-outer-variables-unmodified/exec.js
deleted file mode 100644
index cedc2ee2d7..0000000000
--- a/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-leave-outer-variables-unmodified/exec.js
+++ /dev/null
@@ -1,22 +0,0 @@
-function *gen(x) {
-  var y = x + 1;
-  try {
-    throw x + 2;
-  } catch (x) {
-    yield x;
-    x += 1;
-    yield x;
-  }
-  yield x;
-  try {
-    throw x + 3;
-  } catch (y) {
-    yield y;
-    y *= 2;
-    yield y;
-  }
-  yield y;
-}
-
-genHelpers.check(gen(1), [3, 4, 1, 4, 8, 2]);
-genHelpers.check(gen(2), [4, 5, 2, 5, 10, 3]);
diff --git a/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-not-replace-variables-defined-in-inner-scopes/exec.js b/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-not-replace-variables-defined-in-inner-scopes/exec.js
deleted file mode 100644
index e5e527e3c3..0000000000
--- a/test/fixtures/transformation/es6-generators/catch-parameter-shadowing-should-not-replace-variables-defined-in-inner-scopes/exec.js
+++ /dev/null
@@ -1,32 +0,0 @@
-function *gen(x) {
-  try {
-    throw x;
-  } catch (x) {
-    yield x;
-
-    yield (function(x) {
-      return x += 1;
-    }(x + 1));
-
-    yield (function() {
-      var x = arguments[0];
-      return x * 2;
-    }(x + 2));
-
-    yield (function() {
-      function notCalled(x) {
-        throw x;
-      }
-
-      x >>= 1;
-      return x;
-    }());
-
-    yield x -= 1;
-  }
-
-  yield x;
-}
-
-genHelpers.check(gen(10), [10, 12, 24, 5, 4, 10]);
-genHelpers.check(gen(11), [11, 13, 26, 5, 4, 11]);
diff --git a/test/fixtures/transformation/es6-generators/collatz-generator/exec.js b/test/fixtures/transformation/es6-generators/collatz-generator/exec.js
deleted file mode 100644
index 9bc63db1e9..0000000000
--- a/test/fixtures/transformation/es6-generators/collatz-generator/exec.js
+++ /dev/null
@@ -1,42 +0,0 @@
-function *gen(n) {
-  var count = 0;
-
-  yield n;
-
-  while (n !== 1) {
-    count += 1;
-
-    if (n % 2) {
-      yield n = n * 3 + 1;
-    } else {
-      yield n >>= 1;
-    }
-  }
-
-  return count;
-}
-
-function collatz(n) {
-  var result = [n];
-
-  while (n !== 1) {
-    if (n % 2) {
-      n *= 3;
-      n += 1;
-    } else {
-      n >>= 1;
-    }
-
-    result.push(n);
-  }
-
-  return result;
-}
-
-var seven = collatz(7);
-var fiftyTwo = seven.slice(seven.indexOf(52));
-var eightyTwo = collatz(82);
-
-genHelpers.check(gen(7), seven, 16);
-genHelpers.check(gen(52), fiftyTwo, 11);
-genHelpers.check(gen(82), eightyTwo, 110);
diff --git a/test/fixtures/transformation/es6-generators/completed-generator/exec.js b/test/fixtures/transformation/es6-generators/completed-generator/exec.js
deleted file mode 100644
index 540636d9d3..0000000000
--- a/test/fixtures/transformation/es6-generators/completed-generator/exec.js
+++ /dev/null
@@ -1,11 +0,0 @@
-function *gen() {
-  return "ALL DONE";
-}
-
-var g = gen();
-
-assert.deepEqual(g.next(), {
-  value: "ALL DONE", done: true
-});
-
-genHelpers.assertAlreadyFinished(g);
diff --git a/test/fixtures/transformation/es6-generators/delegated-yield-should-be-governed-by-enclosing-try-statements/exec.js b/test/fixtures/transformation/es6-generators/delegated-yield-should-be-governed-by-enclosing-try-statements/exec.js
deleted file mode 100644
index a4f36ea34b..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yield-should-be-governed-by-enclosing-try-statements/exec.js
+++ /dev/null
@@ -1,27 +0,0 @@
-var error = new Error("thrown");
-
-function *outer(n) {
-  try {
-    yield 0;
-    yield* inner(n);
-    yield 1;
-  } catch (err) {
-    yield err.message;
-  }
-  yield 4;
-}
-
-function *inner(n) {
-  while (n --> 0) {
-    try {
-      if (n === 3) {
-        genHelpers.raise(error);
-      }
-    } finally {
-      yield n;
-    }
-  }
-}
-
-genHelpers.check(outer(3), [0, 2, 1, 0, 1, 4]);
-genHelpers.check(outer(5), [0, 4, 3, "thrown", 4]);
diff --git a/test/fixtures/transformation/es6-generators/delegated-yield-should-cope-with-empty-delegatees/exec.js b/test/fixtures/transformation/es6-generators/delegated-yield-should-cope-with-empty-delegatees/exec.js
deleted file mode 100644
index bf51aa9c8f..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yield-should-cope-with-empty-delegatees/exec.js
+++ /dev/null
@@ -1,10 +0,0 @@
-function *gen(condition) {
-  if (condition) {
-    yield 0;
-    yield* gen(false);
-    yield 1;
-  }
-}
-
-genHelpers.check(gen(true), [0, 1]);
-genHelpers.check(gen(false), []);
diff --git a/test/fixtures/transformation/es6-generators/delegated-yield-should-delegate-correctly/exec.js b/test/fixtures/transformation/es6-generators/delegated-yield-should-delegate-correctly/exec.js
deleted file mode 100644
index 2db0a32fd5..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yield-should-delegate-correctly/exec.js
+++ /dev/null
@@ -1,12 +0,0 @@
-function *gen(condition) {
-  yield 0;
-  if (condition) {
-    yield 1;
-    yield* gen(false);
-    yield 2;
-  }
-  yield 3;
-}
-
-genHelpers.check(gen(true), [0, 1, 0, 3, 2, 3]);
-genHelpers.check(gen(false), [0, 3]);
diff --git a/test/fixtures/transformation/es6-generators/delegated-yield-should-dispatch-thrown-exceptions-correctly/exec.js b/test/fixtures/transformation/es6-generators/delegated-yield-should-dispatch-thrown-exceptions-correctly/exec.js
deleted file mode 100644
index 1dff85c4ab..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yield-should-dispatch-thrown-exceptions-correctly/exec.js
+++ /dev/null
@@ -1,37 +0,0 @@
-var count = 0;
-
-function *gen() {
-  yield* inner();
-  try {
-    yield* inner();
-  } catch (err) {
-    // pass
-  }
-  return yield* inner();
-}
-
-function *inner() {
-  return yield count++;
-}
-
-var g = gen();
-
-assert.deepEqual(g.next(), {
-  value: 0,
-  done: false
-});
-
-assert.deepEqual(g.next(), {
-  value: 1,
-  done: false
-});
-
-assert.deepEqual(g.throw(new Error("lol")), {
-  value: 2,
-  done: false,
-});
-
-assert.deepEqual(g.next("sent"), {
-  value: "sent",
-  done: true
-});
diff --git a/test/fixtures/transformation/es6-generators/delegated-yield-should-pass-sent-values-through/exec.js b/test/fixtures/transformation/es6-generators/delegated-yield-should-pass-sent-values-through/exec.js
deleted file mode 100644
index 1abc3a015a..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yield-should-pass-sent-values-through/exec.js
+++ /dev/null
@@ -1,15 +0,0 @@
-function *outer(n) {
-  yield* inner(n << 1);
-  yield "zxcv";
-}
-
-function *inner(n) {
-  return yield yield yield n;
-}
-
-var g = outer(3);
-assert.deepEqual(g.next(), { value: 6, done: false });
-assert.deepEqual(g.next(1), { value: 1, done: false });
-assert.deepEqual(g.next(2), { value: 2, done: false });
-assert.deepEqual(g.next(4), { value: "zxcv", done: false });
-assert.deepEqual(g.next(5), { value: void 0, done: true });
diff --git a/test/fixtures/transformation/es6-generators/delegated-yield-should-support-deeper-nesting/exec.js b/test/fixtures/transformation/es6-generators/delegated-yield-should-support-deeper-nesting/exec.js
deleted file mode 100644
index f3b8d0f438..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yield-should-support-deeper-nesting/exec.js
+++ /dev/null
@@ -1,18 +0,0 @@
-function *outer(n) {
-  yield n;
-  yield* middle(n - 1, inner(n + 10));
-  yield n + 1;
-}
-
-function *middle(n, plusTen) {
-  yield n;
-  yield* inner(n - 1);
-  yield n + 1;
-  yield* plusTen;
-}
-
-function *inner(n) {
-  yield n;
-}
-
-genHelpers.check(outer(5), [5, 4, 3, 5, 15, 6]);
diff --git a/test/fixtures/transformation/es6-generators/delegated-yieldshould-support-any-iterable-argument/exec.js b/test/fixtures/transformation/es6-generators/delegated-yieldshould-support-any-iterable-argument/exec.js
deleted file mode 100644
index de52f46776..0000000000
--- a/test/fixtures/transformation/es6-generators/delegated-yieldshould-support-any-iterable-argument/exec.js
+++ /dev/null
@@ -1,11 +0,0 @@
-function *gen() {
-  yield 0;
-  yield* [
-    yield "one",
-    yield "two",
-    yield "three"
-  ];
-  yield 5;
-}
-
-genHelpers.check(gen(), [0, "one", "two", "three", 2, 3, 4, 5]);
diff --git a/test/fixtures/transformation/es6-generators/dynamic-exception-should-be-dispatched-correctly/exec.js b/test/fixtures/transformation/es6-generators/dynamic-exception-should-be-dispatched-correctly/exec.js
deleted file mode 100644
index 27a64b3356..0000000000
--- a/test/fixtures/transformation/es6-generators/dynamic-exception-should-be-dispatched-correctly/exec.js
+++ /dev/null
@@ -1,20 +0,0 @@
-function *gen(x, fname) {
-    try {
-      return fns[fname](x);
-    } catch (thrown) {
-      yield thrown;
-    }
-  }
-
-  var fns = {
-    f: function(x) {
-      throw x;
-    },
-
-    g: function(x) {
-      return x;
-    }
-  };
-
-  genHelpers.check(gen("asdf", "f"), ["asdf"]);
-  genHelpers.check(gen("asdf", "g"), [], "asdf");
diff --git a/test/fixtures/transformation/es6-generators/empty-while-loops-should-be-preserved-in-generated-code/exec.js b/test/fixtures/transformation/es6-generators/empty-while-loops-should-be-preserved-in-generated-code/exec.js
deleted file mode 100644
index e762ed9881..0000000000
--- a/test/fixtures/transformation/es6-generators/empty-while-loops-should-be-preserved-in-generated-code/exec.js
+++ /dev/null
@@ -1,16 +0,0 @@
-function *gen(x) {
-  while (x) {
-    // empty while loop
-  }
-
-  do {
-    // empty do-while loop
-  } while (x);
-
-  return gen.toString();
-}
-
-var info = gen(false).next();
-assert.strictEqual(info.done, true);
-assert.ok(/do \{/.test(info.value));
-assert.ok(/while \(/.test(info.value));
diff --git a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-break-in-loop/exec.js b/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-break-in-loop/exec.js
deleted file mode 100644
index e5a2225e7b..0000000000
--- a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-break-in-loop/exec.js
+++ /dev/null
@@ -1,19 +0,0 @@
-function *gen(obj) {
-  var count = 0;
-  for (var key in (yield "why not", obj)) {
-    if (obj.hasOwnProperty(key)) {
-      if (key === "skip") {
-        break;
-      }
-      count += 1;
-      yield [key, obj[key]];
-    }
-  }
-  return count;
-}
-
-genHelpers.check(
-  gen({ a: 1, b: 2, skip: 3, c: 4 }),
-  ["why not", ["a", 1], ["b", 2]],
-  2
-);
diff --git a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-property-deletion-in-loop/exec.js b/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-property-deletion-in-loop/exec.js
deleted file mode 100644
index e0b9313bd7..0000000000
--- a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-property-deletion-in-loop/exec.js
+++ /dev/null
@@ -1,13 +0,0 @@
-function *gen() {
-  var count = 0;
-  var obj = {foo: 1, bar: 2};
-  for (var key in obj) {
-    assert(obj.hasOwnProperty(key), key + " must be own property");
-    yield [key, obj[key]];
-    delete obj.bar;
-    count += 1;
-  }
-  return count;
-}
-
-genHelpers.check(gen(), [["foo", 1]], 1);
diff --git a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-risky-object-expressions/exec.js b/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-risky-object-expressions/exec.js
deleted file mode 100644
index 9fa63ef689..0000000000
--- a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-risky-object-expressions/exec.js
+++ /dev/null
@@ -1,26 +0,0 @@
-function a(sent) {
-  assert.strictEqual(sent, 1);
-  a.called = true;
-}
-
-function b(sent) {
-  assert.strictEqual(sent, 2);
-  b.called = true;
-  return { callee: b };
-}
-
-function *gen() {
-  assert.ok(!a.called);
-  assert.ok(!b.called);
-  for (var key in a(yield 0), b(yield 1)) {
-    assert.ok(a.called);
-    assert.ok(b.called);
-    assert.strictEqual(yield key, 3);
-  }
-
-  for (var key in a(1), { foo: "foo", bar: "bar" }) {
-    yield key;
-  }
-}
-
-genHelpers.check(gen(), [0, 1, "callee", "foo", "bar"]);
diff --git a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-the-simple-case/exec.js b/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-the-simple-case/exec.js
deleted file mode 100644
index 740041c23f..0000000000
--- a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-handle-the-simple-case/exec.js
+++ /dev/null
@@ -1,12 +0,0 @@
-function *gen() {
-  var count = 0;
-  var obj = {foo: 1, bar: 2};
-  for (var key in obj) {
-    assert(obj.hasOwnProperty(key), key + " must be own property");
-    yield [key, obj[key]];
-    count += 1;
-  }
-  return count;
-}
-
-genHelpers.check(gen(), [["foo", 1], ["bar", 2]], 2);
diff --git a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-loop-over-inherited-properties/exec.js b/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-loop-over-inherited-properties/exec.js
deleted file mode 100644
index 1248131d9b..0000000000
--- a/test/fixtures/transformation/es6-generators/for-in-loop-generator-should-loop-over-inherited-properties/exec.js
+++ /dev/null
@@ -1,16 +0,0 @@
-function *gen() {
-  var count = 0;
-  function Foo() {
-    this.baz = 1
-  }
-  Foo.prototype.bar = 2;
-
-  var foo = new Foo();
-  for (var key in foo) {
-    yield [key, foo[key]];
-    count += 1;
-  }
-  return count;
-}
-
-genHelpers.check(gen(), [["baz", 1], ["bar", 2]], 2);
diff --git a/test/fixtures/transformation/es6-generators/for-loop-with-var-decl-and-no-update-expression-should-compile-and-run/exec.js b/test/fixtures/transformation/es6-generators/for-loop-with-var-decl-and-no-update-expression-should-compile-and-run/exec.js
deleted file mode 100644
index 933b61aa3c..0000000000
--- a/test/fixtures/transformation/es6-generators/for-loop-with-var-decl-and-no-update-expression-should-compile-and-run/exec.js
+++ /dev/null
@@ -1,7 +0,0 @@
-// https://github.com/facebook/regenerator/issues/103
-function *range() {
-  for (var i = 0; false; ) {
-  }
-}
-
-genHelpers.check(range(), []);
diff --git a/test/fixtures/transformation/es6-generators/for-of-loops-should-work-for-Arrays/exec.js b/test/fixtures/transformation/es6-generators/for-of-loops-should-work-for-Arrays/exec.js
deleted file mode 100644
index 30b287a0b1..0000000000
--- a/test/fixtures/transformation/es6-generators/for-of-loops-should-work-for-Arrays/exec.js
+++ /dev/null
@@ -1,5 +0,0 @@
-var sum = 0;
-for (var x of [1, 2].concat(3)) {
-  sum += x;
-}
-assert.strictEqual(sum, 6);
diff --git a/test/fixtures/transformation/es6-generators/for-of-loops-should-work-for-generators/exec.js b/test/fixtures/transformation/es6-generators/for-of-loops-should-work-for-generators/exec.js
deleted file mode 100644
index 667e1b67bf..0000000000
--- a/test/fixtures/transformation/es6-generators/for-of-loops-should-work-for-generators/exec.js
+++ /dev/null
@@ -1,10 +0,0 @@
-function *range(n) {
-  for (var i = 0; i < n; ++i) {
-    yield i;
-  }
-}
-
-var value, values = [];
-for (value of range(3))
-  values.push(value);
-assert.deepEqual(values, [0, 1, 2]);
diff --git a/test/fixtures/transformation/es6-generators/for-of-loops-should-work-inside-of-generators/exec.js b/test/fixtures/transformation/es6-generators/for-of-loops-should-work-inside-of-generators/exec.js
deleted file mode 100644
index fda5afe451..0000000000
--- a/test/fixtures/transformation/es6-generators/for-of-loops-should-work-inside-of-generators/exec.js
+++ /dev/null
@@ -1,45 +0,0 @@
-function *yieldPermutations(list) {
-  if (list.length < 2) {
-    yield list;
-    return 1;
-  }
-
-  var count = 0;
-  var first = list.slice(0, 1);
-  var genRest = yieldPermutations(list.slice(1));
-
-  for (var perm of genRest) {
-    for (var i = 0; i < list.length; ++i) {
-      var prefix = perm.slice(0, i);
-      var suffix = perm.slice(i);
-      yield prefix.concat(first, suffix);
-    }
-
-    count += i;
-  }
-
-  return count;
-}
-
-var count = 0;
-for (var perm of yieldPermutations([])) {
-  assert.deepEqual(perm, []);
-  ++count;
-}
-assert.strictEqual(count, 1);
-
-genHelpers.check(yieldPermutations([1]), [[1]], 1);
-
-genHelpers.check(yieldPermutations([2, 1]), [
-  [2, 1],
-  [1, 2]
-], 2);
-
-genHelpers.check(yieldPermutations([1,3,2]), [
-  [1, 3, 2],
-  [3, 1, 2],
-  [3, 2, 1],
-  [1, 2, 3],
-  [2, 1, 3],
-  [2, 3, 1]
-], 6);
diff --git a/test/fixtures/transformation/es6-generators/function-declaration-hoisting-should-work-even-if-the-declarations-are-out-of-order/exec.js b/test/fixtures/transformation/es6-generators/function-declaration-hoisting-should-work-even-if-the-declarations-are-out-of-order/exec.js
deleted file mode 100644
index 1b1de7c33b..0000000000
--- a/test/fixtures/transformation/es6-generators/function-declaration-hoisting-should-work-even-if-the-declarations-are-out-of-order/exec.js
+++ /dev/null
@@ -1,24 +0,0 @@
-function *gen(n) {
-  yield increment(n);
-
-  function increment(x) {
-    return x + 1;
-  }
-
-  if (n % 2) {
-    yield halve(decrement(n));
-
-    function halve(x) {
-      return x >> 1;
-    }
-
-    function decrement(x) {
-      return x - 1;
-    }
-  }
-
-  yield increment(increment(n));
-}
-
-genHelpers.check(gen(3), [4, 1, 5]);
-genHelpers.check(gen(4), [5, 6]);
diff --git a/test/fixtures/transformation/es6-generators/function-declaration-hoisting-should-work-for-nested-generator-function-declarations/exec.js b/test/fixtures/transformation/es6-generators/function-declaration-hoisting-should-work-for-nested-generator-function-declarations/exec.js
deleted file mode 100644
index 62337159e3..0000000000
--- a/test/fixtures/transformation/es6-generators/function-declaration-hoisting-should-work-for-nested-generator-function-declarations/exec.js
+++ /dev/null
@@ -1,15 +0,0 @@
-function *outer(n) {
-  yield 0;
-  assert.ok(regeneratorRuntime.isGeneratorFunction(inner));
-  return yield* inner(n);
-
-  // Note that this function declaration comes after everything else
-  // in the outer function, but needs to be fully available above.
-  function *inner(n) {
-    yield n - 1;
-    yield n;
-    return yield n + 1;
-  }
-}
-
-genHelpers.check(outer(2), [0, 1, 2, 3], 4);
diff --git a/test/fixtures/transformation/es6-generators/generator-function-expression-should-behave-just-like-a-declared-generator/exec.js b/test/fixtures/transformation/es6-generators/generator-function-expression-should-behave-just-like-a-declared-generator/exec.js
deleted file mode 100644
index 6dd8796cb4..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-function-expression-should-behave-just-like-a-declared-generator/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-genHelpers.check(function *(x, y) {
-  yield x;
-  yield y;
-  yield x + y;
-  return x * y;
-}(3, 7), [3, 7, 10], 21);
diff --git a/test/fixtures/transformation/es6-generators/generator-function-prototype-should-follow-the-expected-object-model/exec.js b/test/fixtures/transformation/es6-generators/generator-function-prototype-should-follow-the-expected-object-model/exec.js
deleted file mode 100644
index db35e057a7..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-function-prototype-should-follow-the-expected-object-model/exec.js
+++ /dev/null
@@ -1,60 +0,0 @@
-
-var GeneratorFunctionPrototype = f.__proto__;
-var GeneratorFunction = GeneratorFunctionPrototype.constructor;
-
-assert.strictEqual(GeneratorFunction.name, 'GeneratorFunction');
-assert.strictEqual(GeneratorFunction.prototype,
-                   GeneratorFunctionPrototype);
-assert.strictEqual(GeneratorFunctionPrototype.prototype.constructor,
-                   GeneratorFunctionPrototype);
-assert.strictEqual(GeneratorFunctionPrototype.prototype,
-                   f.prototype.__proto__);
-assert.strictEqual(GeneratorFunctionPrototype.__proto__,
-                   Function.prototype);
-assert.strictEqual(GeneratorFunctionPrototype.name,
-                   "GeneratorFunctionPrototype");
-
-assert.strictEqual(typeof f2, "function");
-assert.strictEqual(f2.constructor, GeneratorFunction);
-assert.ok(f2 instanceof GeneratorFunction);
-assert.strictEqual(f2.name, "f2");
-
-var g = f();
-assert.ok(g instanceof f);
-assert.strictEqual(g.__proto__, f.prototype);
-
-assert.deepEqual([], Object.getOwnPropertyNames(f.prototype));
-// assert.deepEqual([], Object.getOwnPropertyNames(g));
-
-f.prototype.x = 42;
-
-var g2 = f();
-assert.strictEqual(g2.x, 42);
-
-var g3 = new f();
-assert.strictEqual(g3.x, 42);
-
-function* f2() {
-  yield 1;
-}
-
-assert.strictEqual(f.__proto__, f2.__proto__);
-assert.strictEqual(f.hasOwnProperty('constructor'), false);
-assert.strictEqual(f.__proto__.constructor.name, 'GeneratorFunction');
-
-// Intentionally at the end to test hoisting.
-function* f() {
-  yield this;
-}
-
-function* f() {
-  yield 1;
-}
-
-var f2 = f;
-f = 42;
-var g = f2();
-
-assert.deepEqual(g.next(), { value: 1, done: false });
-assert.deepEqual(g.next(), { value: void 0, done: true });
-assert.ok(g instanceof f2);
diff --git a/test/fixtures/transformation/es6-generators/generator-reentry-attempt-should-complain-with-a-TypeError/exec.js b/test/fixtures/transformation/es6-generators/generator-reentry-attempt-should-complain-with-a-TypeError/exec.js
deleted file mode 100644
index ce41e9851e..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-reentry-attempt-should-complain-with-a-TypeError/exec.js
+++ /dev/null
@@ -1,18 +0,0 @@
-function *gen(x) {
-  try {
-    (yield x).next(x);
-  } catch (err) {
-    yield err;
-  }
-  return x + 1;
-}
-
-var g = gen(3);
-assert.deepEqual(g.next(), { value: 3, done: false });
-var complaint = g.next(g); // Sending the generator to itself.
-assert.ok(complaint.value instanceof Error);
-assert.strictEqual(
-  complaint.value.message,
-  "Generator is already running"
-);
-assert.deepEqual(g.next(), { value: 4, done: true });
diff --git a/test/fixtures/transformation/es6-generators/generator-return-method-should-behave-as-if-generator-actually-returned/exec.js b/test/fixtures/transformation/es6-generators/generator-return-method-should-behave-as-if-generator-actually-returned/exec.js
deleted file mode 100644
index 089deed534..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-return-method-should-behave-as-if-generator-actually-returned/exec.js
+++ /dev/null
@@ -1,22 +0,0 @@
-var executedFinally = false;
-
-function *gen() {
-  try {
-    yield 0;
-  } catch (err) {
-    assert.ok(false, "should not have executed the catch handler");
-  } finally {
-    executedFinally = true;
-  }
-}
-
-var g = gen();
-assert.deepEqual(g.next(), { value: 0, done: false });
-
-assert.deepEqual(g.return("argument"), {
-  value: "argument",
-  done: true
-});
-
-assert.strictEqual(executedFinally, true);
-genHelpers.assertAlreadyFinished(g);
diff --git a/test/fixtures/transformation/es6-generators/generator-return-method-should-work-with-newborn-generators/exec.js b/test/fixtures/transformation/es6-generators/generator-return-method-should-work-with-newborn-generators/exec.js
deleted file mode 100644
index 84f60dbf8f..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-return-method-should-work-with-newborn-generators/exec.js
+++ /dev/null
@@ -1,12 +0,0 @@
-function *gen() {
-  yield 0;
-}
-
-var g = gen();
-
-assert.deepEqual(g.return("argument"), {
-  value: "argument",
-  done: true
-});
-
-genHelpers.assertAlreadyFinished(g);
diff --git a/test/fixtures/transformation/es6-generators/generator-throw-method-should-complete-generator/exec.js b/test/fixtures/transformation/es6-generators/generator-throw-method-should-complete-generator/exec.js
deleted file mode 100644
index c41c82c2dd..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-throw-method-should-complete-generator/exec.js
+++ /dev/null
@@ -1,16 +0,0 @@
-function *gen(x) {
-  yield 2;
-  throw 1;
-}
-
-var u = gen();
-
-u.next();
-
-try {
-  u.throw(2);
-} catch (err) {
-  assert.strictEqual(err, 2);
-}
-
-genHelpers.assertAlreadyFinished(u);
diff --git a/test/fixtures/transformation/es6-generators/generator-throw-method-should-immediately-complete-a-new-born-generator/exec.js b/test/fixtures/transformation/es6-generators/generator-throw-method-should-immediately-complete-a-new-born-generator/exec.js
deleted file mode 100644
index 175435b562..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-throw-method-should-immediately-complete-a-new-born-generator/exec.js
+++ /dev/null
@@ -1,16 +0,0 @@
-var began = false;
-
-function *gen() {
-  began = true;
-  yield 1;
-}
-
-var g = gen();
-var exception = new Error("unhandled exception");
-try {
-  g.throw(exception);
-  assert.ok(false, "should have thrown an exception");
-} catch (err) {
-  assert.strictEqual(err, exception);
-  assert.strictEqual(began, false);
-}
diff --git a/test/fixtures/transformation/es6-generators/generator-throw-method-should-not-propagate-errors-handled-inside-a-delegate/exec.js b/test/fixtures/transformation/es6-generators/generator-throw-method-should-not-propagate-errors-handled-inside-a-delegate/exec.js
deleted file mode 100644
index dcdce48792..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-throw-method-should-not-propagate-errors-handled-inside-a-delegate/exec.js
+++ /dev/null
@@ -1,20 +0,0 @@
-function *outer() {
-  try {
-    yield* inner();
-  } catch (err) {
-    return -1;
-  }
-  return 1;
-}
-
-function *inner() {
-  try {
-    yield void 0;
-  } catch (e) {
-    return;
-  }
-}
-
-var g = outer();
-g.next();
-assert.equal(g.throw(new Error('foo')).value, 1);
diff --git a/test/fixtures/transformation/es6-generators/generator-throw-method-should-propagate-errors-unhandled-inside-a-delegate/exec.js b/test/fixtures/transformation/es6-generators/generator-throw-method-should-propagate-errors-unhandled-inside-a-delegate/exec.js
deleted file mode 100644
index 295a4c8aeb..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-throw-method-should-propagate-errors-unhandled-inside-a-delegate/exec.js
+++ /dev/null
@@ -1,16 +0,0 @@
-function *outer() {
-  try {
-    yield* inner();
-  } catch (err) {
-    return -1;
-  }
-  return 1;
-}
-
-function *inner() {
-  yield void 0;
-}
-
-var g = outer();
-g.next();
-assert.equal(g.throw(new Error('foo')).value, -1);
diff --git a/test/fixtures/transformation/es6-generators/generator-throw-method-should-work-after-the-final-call-to-next/exec.js b/test/fixtures/transformation/es6-generators/generator-throw-method-should-work-after-the-final-call-to-next/exec.js
deleted file mode 100644
index 7017683f5e..0000000000
--- a/test/fixtures/transformation/es6-generators/generator-throw-method-should-work-after-the-final-call-to-next/exec.js
+++ /dev/null
@@ -1,14 +0,0 @@
-function *gen() {
-  yield 1;
-}
-
-var g = gen();
-assert.deepEqual(g.next(), { value: 1, done: false });
-
-var exception = new Error("unhandled exception");
-try {
-  g.throw(exception);
-  assert.ok(false, "should have thrown an exception");
-} catch (err) {
-  assert.strictEqual(err, exception);
-}
diff --git a/test/fixtures/transformation/es6-generators/infinite-sequence-generator/exec.js b/test/fixtures/transformation/es6-generators/infinite-sequence-generator/exec.js
deleted file mode 100644
index 7c74586b83..0000000000
--- a/test/fixtures/transformation/es6-generators/infinite-sequence-generator/exec.js
+++ /dev/null
@@ -1,41 +0,0 @@
-function *gen(start, step) {
-  step = step || 1;
-  while (true) {
-    yield start;
-    start += step;
-  }
-}
-
-function *limit(g, stop) {
-  while (true) {
-    var info = g.next();
-    if (info.done) {
-      return;
-    } else if (info.value < stop) {
-      yield info.value;
-    } else {
-      return;
-    }
-  }
-}
-
-// should generate a lot of plausible values
-var g = gen(10, 2);
-
-assert.deepEqual(g.next(), { value: 10, done: false });
-assert.deepEqual(g.next(), { value: 12, done: false });
-assert.deepEqual(g.next(), { value: 14, done: false });
-assert.deepEqual(g.next(), { value: 16, done: false });
-
-var sum = 10 + 12 + 14 + 16;
-
-for (var n = 0; n < 1000; ++n) {
-  var info = g.next();
-  sum += info.value;
-  assert.strictEqual(info.done, false);
-}
-
-assert.strictEqual(sum, 1017052);
-
-// should allow limiting
-genHelpers.check(limit(gen(10, 3), 20), [10, 13, 16, 19]);
diff --git a/test/fixtures/transformation/es6-generators/isGeneratorFunction-should-work-for-function-declarations/exec.js b/test/fixtures/transformation/es6-generators/isGeneratorFunction-should-work-for-function-declarations/exec.js
deleted file mode 100644
index daebbf16da..0000000000
--- a/test/fixtures/transformation/es6-generators/isGeneratorFunction-should-work-for-function-declarations/exec.js
+++ /dev/null
@@ -1,19 +0,0 @@
-// Do the assertions up here to make sure the generator function is
-// marked at the beginning of the block the function is declared in.
-assert.strictEqual(
-  regeneratorRuntime.isGeneratorFunction(genFun),
-  true
-);
-
-assert.strictEqual(
-  regeneratorRuntime.isGeneratorFunction(normalFun),
-  false
-);
-
-function normalFun() {
-  return 0;
-}
-
-function *genFun() {
-  yield 0;
-}
diff --git a/test/fixtures/transformation/es6-generators/isGeneratorFunction-should-work-for-function-expressions/exec.js b/test/fixtures/transformation/es6-generators/isGeneratorFunction-should-work-for-function-expressions/exec.js
deleted file mode 100644
index a7649e0737..0000000000
--- a/test/fixtures/transformation/es6-generators/isGeneratorFunction-should-work-for-function-expressions/exec.js
+++ /dev/null
@@ -1,13 +0,0 @@
-assert.strictEqual(
-  regeneratorRuntime.isGeneratorFunction(function *genFun() {
-    yield 0;
-  }),
-  true
-);
-
-assert.strictEqual(
-  regeneratorRuntime.isGeneratorFunction(function normalFun() {
-    return 0;
-  }),
-  false
-);
diff --git a/test/fixtures/transformation/es6-generators/labeled-break-and-continue-statements-should-be-able-to-exit-multiple-try-statements/exec.js b/test/fixtures/transformation/es6-generators/labeled-break-and-continue-statements-should-be-able-to-exit-multiple-try-statements/exec.js
deleted file mode 100644
index 3bf4008ebe..0000000000
--- a/test/fixtures/transformation/es6-generators/labeled-break-and-continue-statements-should-be-able-to-exit-multiple-try-statements/exec.js
+++ /dev/null
@@ -1,82 +0,0 @@
-
-    var e1 = "first";
-    var e2 = "second";
-    var e3 = "third";
-    var e4 = "fourth";
-
-    function *gen(n, which) {
-      try {
-        yield 0;
-        genHelpers.raise(e1);
-
-      } finally {
-        yield 1;
-
-        loop:
-        for (var i = 0; i < n; ++i) {
-          yield i;
-
-          try {
-            genHelpers.raise(e2);
-          } finally {
-            yield 2;
-
-            try {
-              genHelpers.raise(e3);
-            } finally {
-              yield 3;
-
-              try {
-                genHelpers.raise(e4);
-              } finally {
-                yield 4;
-
-                if (which === "break") {
-                  yield "breaking";
-                  break loop;
-                }
-
-                if (which === "continue") {
-                  yield "continuing";
-                  continue loop;
-                }
-
-                yield 5;
-              }
-            }
-          }
-        }
-
-        yield 6;
-      }
-    }
-
-    try {
-      genHelpers.check(gen(1, "break"), [
-        0, 1, 0, 2, 3, 4, "breaking", 6
-      ]);
-      assert.ok(false, "should have thrown an exception");
-    } catch (err) {
-      assert.strictEqual(err, e1);
-    }
-
-    try {
-      genHelpers.check(gen(3, "continue"), [
-        0, 1, 0, 2, 3, 4, "continuing",
-        1, 2, 3, 4, "continuing",
-        2, 2, 3, 4, "continuing",
-        6 // Loop finished naturally.
-      ]);
-      assert.ok(false, "should have thrown an exception");
-    } catch (err) {
-      assert.strictEqual(err, e1);
-    }
-
-    try {
-      genHelpers.check(gen(3, "neither"), [
-        0, 1, 0, 2, 3, 4, 5
-      ]);
-      assert.ok(false, "should have thrown an exception");
-    } catch (err) {
-      assert.strictEqual(err, e4);
-    }
diff --git a/test/fixtures/transformation/es6-generators/nested-finally-blocks/exec.js b/test/fixtures/transformation/es6-generators/nested-finally-blocks/exec.js
deleted file mode 100644
index 1bcdee5b49..0000000000
--- a/test/fixtures/transformation/es6-generators/nested-finally-blocks/exec.js
+++ /dev/null
@@ -1,41 +0,0 @@
-function *usingThrow() {
-  try {
-    try {
-      try {
-        throw "thrown";
-      } finally {
-        yield 1;
-      }
-    } catch (thrown) {
-      yield thrown;
-    } finally {
-      yield 2;
-    }
-  } finally {
-    yield 3;
-  }
-}
-
-function *usingRaise() {
-  try {
-    try {
-      try {
-        genHelpers.raise("thrown");
-      } finally {
-        yield 1;
-      }
-    } catch (thrown) {
-      yield thrown;
-    } finally {
-      yield 2;
-    }
-  } finally {
-    yield 3;
-  }
-}
-
-// should statically execute in order
-genHelpers.check(usingThrow(), [1, "thrown", 2, 3]);
-
-// should dynamically execute in order
-genHelpers.check(usingRaise(), [1, "thrown", 2, 3]);
diff --git a/test/fixtures/transformation/es6-generators/nested-generators-in-try-catch-should-get-a-reference-to-the-caught-error/exec.js b/test/fixtures/transformation/es6-generators/nested-generators-in-try-catch-should-get-a-reference-to-the-caught-error/exec.js
deleted file mode 100644
index f585b20cba..0000000000
--- a/test/fixtures/transformation/es6-generators/nested-generators-in-try-catch-should-get-a-reference-to-the-caught-error/exec.js
+++ /dev/null
@@ -1,18 +0,0 @@
-function *gen() {
-  try {
-     nonExistent;
-  } catch (e) {
-    yield function* () {
-      yield e;
-    }
-  }
-}
-
-var genFun2 = gen().next().value;
-assert.ok(regeneratorRuntime.isGeneratorFunction(genFun2));
-var gen2 = genFun2();
-var res = gen2.next();
-assert.ok(res.value instanceof ReferenceError);
-// Note that we don't do strict equality over the message because it varies
-// across browsers (if we ever want to run tests in browsers).
-assert.ok(res.value.message.match(/nonExistent/));
diff --git a/test/fixtures/transformation/es6-generators/new-expressions-should-be-able-to-contain-yield-sub-expressions/exec.js b/test/fixtures/transformation/es6-generators/new-expressions-should-be-able-to-contain-yield-sub-expressions/exec.js
deleted file mode 100644
index 6435d69531..0000000000
--- a/test/fixtures/transformation/es6-generators/new-expressions-should-be-able-to-contain-yield-sub-expressions/exec.js
+++ /dev/null
@@ -1,22 +0,0 @@
-function A(first, second) {
-  this.first = first;
-  this.second = second;
-}
-
-function *gen() {
-  return yield new (yield 0)(yield 1, yield 2);
-}
-
-var g = gen();
-
-assert.deepEqual(g.next(), { value: 0, done: false });
-assert.deepEqual(g.next(A), { value: 1, done: false });
-assert.deepEqual(g.next("asdf"), { value: 2, done: false });
-
-var info = g.next("zxcv");
-assert.strictEqual(info.done, false);
-assert.ok(info.value instanceof A);
-assert.strictEqual(info.value.first, "asdf");
-assert.strictEqual(info.value.second, "zxcv");
-
-assert.deepEqual(g.next("qwer"), { value: "qwer", done: true });
diff --git a/test/fixtures/transformation/es6-generators/newborn-generators-should-allow-chaining-newborn-and-non-newborn-generators/exec.js b/test/fixtures/transformation/es6-generators/newborn-generators-should-allow-chaining-newborn-and-non-newborn-generators/exec.js
deleted file mode 100644
index 630120638b..0000000000
--- a/test/fixtures/transformation/es6-generators/newborn-generators-should-allow-chaining-newborn-and-non-newborn-generators/exec.js
+++ /dev/null
@@ -1,40 +0,0 @@
-function *range(n) {
-  for (var i = 0; i < n; ++i) {
-    yield i;
-  }
-}
-
-function *chain(a, b) {
-  yield* a;
-  yield* b;
-}
-
-genHelpers.check(chain(range(3), range(5)), [0, 1, 2, 0, 1, 2, 3, 4]);
-
-function *y3(x) {
-  return yield yield yield x;
-}
-
-function *y5(x) {
-  return yield yield yield yield yield x;
-}
-
-genHelpers.check(
-  chain(y3("foo"), y5("bar")),
-  ["foo", 1, 2, "bar", 4, 5, 6, 7]
-);
-
-var g3 = y3("three");
-assert.deepEqual(g3.next(), {
-  value: "three",
-  done: false
-});
-
-var g5 = y5("five");
-assert.deepEqual(g5.next(), {
-  value: "five",
-  done: false
-});
-
-var undef; // A little easier to read than void 0.
-genHelpers.check(chain(g3, g5), [undef, 1, undef, 3, 4, 5]);
diff --git a/test/fixtures/transformation/es6-generators/newborn-generators-should-be-able-to-yield-star-non-newborn-generators/exec.js b/test/fixtures/transformation/es6-generators/newborn-generators-should-be-able-to-yield-star-non-newborn-generators/exec.js
deleted file mode 100644
index 9d8d186519..0000000000
--- a/test/fixtures/transformation/es6-generators/newborn-generators-should-be-able-to-yield-star-non-newborn-generators/exec.js
+++ /dev/null
@@ -1,29 +0,0 @@
-function *inner() {
-  return [yield 1, yield 2];
-}
-
-function *outer(delegate) {
-  return yield* delegate;
-}
-
-var n = inner();
-
-assert.deepEqual(n.next(), {
-  value: 1,
-  done: false
-});
-
-var g = outer(n);
-
-// I would really like to be able to pass 3 to g.next here, but V8
-// ignores values sent to newborn generators, and SpiderMonkey throws
-// a TypeError.
-assert.deepEqual(g.next(), {
-  value: 2,
-  done: false
-});
-
-assert.deepEqual(g.next(4), {
-  value: [void 0, 4],
-  done: true
-});
diff --git a/test/fixtures/transformation/es6-generators/newborn-generators-should-support-the-ignore-initial-yield-wrapper-idiom/exec.js b/test/fixtures/transformation/es6-generators/newborn-generators-should-support-the-ignore-initial-yield-wrapper-idiom/exec.js
deleted file mode 100644
index 2eb492c895..0000000000
--- a/test/fixtures/transformation/es6-generators/newborn-generators-should-support-the-ignore-initial-yield-wrapper-idiom/exec.js
+++ /dev/null
@@ -1,58 +0,0 @@
-var markers = [];
-
-function *inner() {
-  markers.push(0);
-  var sent1 = yield 1;
-  markers.push(2);
-  var sent2 = yield 2;
-  markers.push(3);
-  return [sent1, sent2];
-}
-
-function wrapper(delegate) {
-  var gen = (function*() {
-    // This yield is the "initial yield" whose argument we ignore.
-    var sent = yield "ignored", info;
-
-    markers.push(1);
-
-    while (!(info = delegate.next(sent)).done) {
-      sent = yield info.value;
-    }
-
-    markers.push(4);
-
-    return info.value;
-  })();
-
-  // Ensure that gen is not newborn and that the next invocation of
-  // gen.next(value) can send value to the initial yield expression.
-  gen.next();
-
-  return gen;
-}
-
-var n = inner();
-
-assert.deepEqual(n.next(), {
-  value: 1,
-  done: false
-});
-
-var g = wrapper(n);
-
-// Unlike in the previous spec, it's fine to pass 3 to g.next here,
-// because g is not newborn, because g.next was already called once
-// before g was returned from the wrapper function.
-assert.deepEqual(g.next(3), {
-  value: 2,
-  done: false
-});
-
-assert.deepEqual(g.next(4), {
-  value: [3, 4],
-  done: true
-});
-
-// Ensure we encountered the marker points in the expected order.
-assert.deepEqual(markers, [0, 1, 2, 3, 4]);
diff --git a/test/fixtures/transformation/es6-generators/object-literal-generator-should-yield-the-correct-object/exec.js b/test/fixtures/transformation/es6-generators/object-literal-generator-should-yield-the-correct-object/exec.js
deleted file mode 100644
index a45a519ba8..0000000000
--- a/test/fixtures/transformation/es6-generators/object-literal-generator-should-yield-the-correct-object/exec.js
+++ /dev/null
@@ -1,9 +0,0 @@
-function *gen(a, b) {
-  yield {
-    a: a - (yield a),
-    b: yield b
-  };
-}
-
-genHelpers.check(gen(1, 2), [1, 2, { a: 0, b: 2 }]);
-genHelpers.check(gen(4, 2), [4, 2, { a: 3, b: 2 }]);
diff --git a/test/fixtures/transformation/es6-generators/object-literals-with-multiple-yields-should-receive-different-sent-values/exec.js b/test/fixtures/transformation/es6-generators/object-literals-with-multiple-yields-should-receive-different-sent-values/exec.js
deleted file mode 100644
index e18ec96410..0000000000
--- a/test/fixtures/transformation/es6-generators/object-literals-with-multiple-yields-should-receive-different-sent-values/exec.js
+++ /dev/null
@@ -1,17 +0,0 @@
-function *gen(fn) {
-  return {
-    a: yield "a",
-    b: yield "b",
-    c: fn(yield "c", yield "d"),
-    d: [yield "e", yield "f"]
-  };
-}
-
-genHelpers.check(gen(function sum(x, y) {
-  return x + y;
-}), ["a", "b", "c", "d", "e", "f"], {
-  a: 1,
-  b: 2,
-  c: 3 + 4,
-  d: [5, 6]
-});
diff --git a/test/fixtures/transformation/es6-generators/range-generator/exec.js b/test/fixtures/transformation/es6-generators/range-generator/exec.js
deleted file mode 100644
index eef007c261..0000000000
--- a/test/fixtures/transformation/es6-generators/range-generator/exec.js
+++ /dev/null
@@ -1,9 +0,0 @@
-function *range(n) {
-  for (var i = 0; i < n; ++i) {
-    yield i;
-  }
-}
-
-genHelpers.check(range(0), []);
-
-genHelpers.check(range(5), [0, 1, 2, 3, 4]);
diff --git a/test/fixtures/transformation/es6-generators/should-support-multiple-yields-in-expression/exec.js b/test/fixtures/transformation/es6-generators/should-support-multiple-yields-in-expression/exec.js
deleted file mode 100644
index 07ea21e280..0000000000
--- a/test/fixtures/transformation/es6-generators/should-support-multiple-yields-in-expression/exec.js
+++ /dev/null
@@ -1,5 +0,0 @@
-function *gen() { return (yield 0) + (yield 0); }
-var itr = gen();
-itr.next();
-itr.next(1);
-assert.equal(itr.next(2).value, 3);
diff --git a/test/fixtures/transformation/es6-generators/should-yield-only-its-first-argument/exec.js b/test/fixtures/transformation/es6-generators/should-yield-only-its-first-argument/exec.js
deleted file mode 100644
index d872a6c160..0000000000
--- a/test/fixtures/transformation/es6-generators/should-yield-only-its-first-argument/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-function *gen(x) {
-  yield x;
-}
-
-genHelpers.check(gen("oyez"), ["oyez"]);
-genHelpers.check(gen("foo", "bar"), ["foo"]);
diff --git a/test/fixtures/transformation/es6-generators/switch-statement-generator-should-jump-to-the-correct-cases/exec.js b/test/fixtures/transformation/es6-generators/switch-statement-generator-should-jump-to-the-correct-cases/exec.js
deleted file mode 100644
index f506e3dc92..0000000000
--- a/test/fixtures/transformation/es6-generators/switch-statement-generator-should-jump-to-the-correct-cases/exec.js
+++ /dev/null
@@ -1,11 +0,0 @@
-function *gen(a) {
-  switch (yield a) {
-  case (yield "x") - a:
-    return "first case";
-  case (yield "y") - a:
-    return "second case";
-  }
-}
-
-genHelpers.check(gen(1), [1, "x"], "first case");
-genHelpers.check(gen(2), [2, "x", "y"], "second case");
diff --git a/test/fixtures/transformation/es6-generators/the-arguments-object-should-not-get-confused-by-properties/exec.js b/test/fixtures/transformation/es6-generators/the-arguments-object-should-not-get-confused-by-properties/exec.js
deleted file mode 100644
index 0193713567..0000000000
--- a/test/fixtures/transformation/es6-generators/the-arguments-object-should-not-get-confused-by-properties/exec.js
+++ /dev/null
@@ -1,7 +0,0 @@
-function *gen(obj) {
-  yield obj.arguments;
-  obj.arguments = "oyez";
-  yield obj;
-}
-
-genHelpers.check(gen({ arguments: 42 }), [42, { arguments: "oyez" }]);
diff --git a/test/fixtures/transformation/es6-generators/the-arguments-object-should-work-in-simple-variadic-functions/exec.js b/test/fixtures/transformation/es6-generators/the-arguments-object-should-work-in-simple-variadic-functions/exec.js
deleted file mode 100644
index 2082baecd9..0000000000
--- a/test/fixtures/transformation/es6-generators/the-arguments-object-should-work-in-simple-variadic-functions/exec.js
+++ /dev/null
@@ -1,12 +0,0 @@
-function *sum() {
-  var result = 0;
-
-  for (var i = 0; i < arguments.length; ++i) {
-    yield result += arguments[i];
-  }
-
-  return result;
-}
-
-genHelpers.check(sum(1, 2, 3), [1, 3, 6], 6);
-genHelpers.check(sum(9, -5, 3, 0, 2), [9, 4, 7, 7, 9], 9);
diff --git a/test/fixtures/transformation/es6-generators/throw-should-complete-generator/exec.js b/test/fixtures/transformation/es6-generators/throw-should-complete-generator/exec.js
deleted file mode 100644
index aeba49f47d..0000000000
--- a/test/fixtures/transformation/es6-generators/throw-should-complete-generator/exec.js
+++ /dev/null
@@ -1,13 +0,0 @@
-function *gen(x) {
-  throw 1;
-}
-
-var u = gen();
-
-try {
-  u.next();
-} catch (err) {
-  assert.strictEqual(err, 1);
-}
-
-genHelpers.assertAlreadyFinished(u);
diff --git a/test/fixtures/transformation/es6-generators/try-catch-finally-generator/exec.js b/test/fixtures/transformation/es6-generators/try-catch-finally-generator/exec.js
deleted file mode 100644
index 5c25e461bd..0000000000
--- a/test/fixtures/transformation/es6-generators/try-catch-finally-generator/exec.js
+++ /dev/null
@@ -1,42 +0,0 @@
-
-  function *usingThrow() {
-    yield 0;
-    try {
-      try {
-        yield 1;
-        throw 2;
-        yield 3;
-      } catch (x) {
-        throw yield x;
-      } finally {
-        yield 5;
-      }
-    } catch (thrown) {
-      yield thrown;
-    }
-    yield 6;
-  }
-
-  function *usingRaise() {
-    yield 0;
-    try {
-      try {
-        yield 1;
-        genHelpers.raise(2);
-        yield 3;
-      } catch (x) {
-        throw yield x;
-      } finally {
-        yield 5;
-      }
-    } catch (thrown) {
-      yield thrown;
-    }
-    yield 6;
-  }
-
-  // should statically catch and then finalize
-  genHelpers.check(usingThrow(), [0, 1, 2, 5, 3, 6]);
-
-  // should dynamically catch and then finalize
-  genHelpers.check(usingRaise(), [0, 1, 2, 5, 3, 6]);
diff --git a/test/fixtures/transformation/es6-generators/try-catch-generator/exec.js b/test/fixtures/transformation/es6-generators/try-catch-generator/exec.js
deleted file mode 100644
index 67ce947eab..0000000000
--- a/test/fixtures/transformation/es6-generators/try-catch-generator/exec.js
+++ /dev/null
@@ -1,33 +0,0 @@
-function *usingThrow(x) {
-  yield 0;
-  try {
-    yield 1;
-    if (x % 2 === 0)
-      throw 2;
-    yield x;
-  } catch (x) {
-    yield x;
-  }
-  yield 3;
-}
-
-function *usingRaise(x) {
-  yield 0;
-  try {
-    yield 1;
-    if (x % 2 === 0)
-      genHelpers.raise(2);
-    yield x;
-  } catch (x) {
-    yield x;
-  }
-  yield 3;
-}
-
-// should catch static exceptions properly
-genHelpers.check(usingThrow(4), [0, 1, 2, 3]);
-genHelpers.check(usingThrow(5), [0, 1, 5, 3]);
-
-// should catch dynamic exceptions properly
-genHelpers.check(usingRaise(4), [0, 1, 2, 3]);
-genHelpers.check(usingRaise(5), [0, 1, 5, 3]);
diff --git a/test/fixtures/transformation/es6-generators/try-finally-generator/exec.js b/test/fixtures/transformation/es6-generators/try-finally-generator/exec.js
deleted file mode 100644
index 889aa259cc..0000000000
--- a/test/fixtures/transformation/es6-generators/try-finally-generator/exec.js
+++ /dev/null
@@ -1,114 +0,0 @@
-function *usingThrow(condition) {
-  yield 0;
-  try {
-    yield 1;
-    throw 2;
-    yield 3;
-  } finally {
-    if (condition) {
-      yield 4;
-      return 5;
-    }
-    yield 6;
-    return 7;
-  }
-}
-
-function *usingRaise(condition) {
-  yield 0;
-  try {
-    yield 1;
-    genHelpers.raise(2);
-    yield 3;
-  } finally {
-    if (condition) {
-      yield 4;
-      return 5;
-    }
-    yield 6;
-    return 7;
-  }
-}
-
-// should execute finally blocks statically
-genHelpers.check(usingThrow(true), [0, 1, 4], 5);
-genHelpers.check(usingThrow(false), [0, 1, 6], 7);
-
-// should execute finally blocks dynamically
-genHelpers.check(usingRaise(true), [0, 1, 4], 5);
-genHelpers.check(usingRaise(false), [0, 1, 6], 7);
-
-// should execute finally blocks before throwing
-var uncaughtError = new Error("uncaught");
-
-function *uncaught(condition) {
-  try {
-    yield 0;
-    if (condition) {
-      yield 1;
-      genHelpers.raise(uncaughtError);
-    }
-    yield 2;
-  } finally {
-    yield 3;
-  }
-  yield 4;
-}
-
-genHelpers.check(uncaught(false), [0, 2, 3, 4]);
-
-var u = uncaught(true);
-
-assert.deepEqual(u.next(), { value: 0, done: false });
-assert.deepEqual(u.next(), { value: 1, done: false });
-assert.deepEqual(u.next(), { value: 3, done: false });
-
-try {
-  u.next();
-  assert.ok(false, "should have thrown an exception");
-} catch (err) {
-  assert.strictEqual(err, uncaughtError);
-}
-
-// should throw correct error when finally contains catch
-var right = new Error("right");
-var wrong = new Error("wrong");
-
-function *gen() {
-  try {
-    yield 0;
-    genHelpers.raise(right);
-  } finally {
-    yield 1;
-    try {
-      genHelpers.raise(wrong);
-    } catch (err) {
-      assert.strictEqual(err, wrong);
-      yield 2;
-    }
-  }
-}
-
-var g = gen();
-
-assert.deepEqual(g.next(), {
-  value: 0,
-  done: false
-});
-
-assert.deepEqual(g.next(), {
-  value: 1,
-  done: false
-});
-
-assert.deepEqual(g.next(), {
-  value: 2,
-  done: false
-});
-
-try {
-  g.next();
-  assert.ok(false, "should have thrown an exception");
-} catch (err) {
-  assert.strictEqual(err, right);
-}
diff --git a/test/fixtures/transformation/es6-generators/unqualified-function-calls-should-have-a-global-`this`-object/exec.js b/test/fixtures/transformation/es6-generators/unqualified-function-calls-should-have-a-global-`this`-object/exec.js
deleted file mode 100644
index 35f5677b77..0000000000
--- a/test/fixtures/transformation/es6-generators/unqualified-function-calls-should-have-a-global-`this`-object/exec.js
+++ /dev/null
@@ -1,26 +0,0 @@
-function getThis() {
-  return this;
-}
-
-// This is almost certainly the global object, but there's a chance it
-// might be null or undefined (in strict mode).
-var unqualifiedThis = getThis();
-
-function *invoke() {
-  // It seems like a bug in the ES6 spec that we have to yield an
-  // argument instead of just calling (yield)().
-  return (yield "dummy")();
-}
-
-var g = invoke();
-var info = g.next();
-
-assert.deepEqual(info, { value: "dummy", done: false });
-
-info = g.next(getThis);
-
-// Avoid using assert.strictEqual when the arguments might equal the
-// global object, since JSON.stringify chokes on circular structures.
-assert.ok(info.value === unqualifiedThis);
-
-assert.strictEqual(info.done, true);
diff --git a/test/fixtures/transformation/es6-generators/yield-chain-should-have-correct-associativity/exec.js b/test/fixtures/transformation/es6-generators/yield-chain-should-have-correct-associativity/exec.js
deleted file mode 100644
index 5918d1c894..0000000000
--- a/test/fixtures/transformation/es6-generators/yield-chain-should-have-correct-associativity/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-function *gen(n) {
-  return yield yield yield yield n;
-}
-
-genHelpers.check(gen(5), [5, 1, 2, 3], 4);
-genHelpers.check(gen("asdf"), ["asdf", 1, 2, 3], 4);
diff --git a/test/fixtures/transformation/es6-generators/yield-star-expression-results-can-be-used-in-complex-expressions/exec.js b/test/fixtures/transformation/es6-generators/yield-star-expression-results-can-be-used-in-complex-expressions/exec.js
deleted file mode 100644
index ffe646947a..0000000000
--- a/test/fixtures/transformation/es6-generators/yield-star-expression-results-can-be-used-in-complex-expressions/exec.js
+++ /dev/null
@@ -1,22 +0,0 @@
-function pumpNumber(gen) {
-  var n = 0;
-
-  while (true) {
-    var res = n > 0 ? gen.next(n) : gen.next();
-    n = res.value;
-    if (res.done) {
-      return n;
-    }
-  }
-}
-
-function* foo() {
-  return (yield* bar()) + (yield* bar());
-}
-
-function* bar() {
-  return (yield 2) + (yield 3);
-}
-
-assert.strictEqual(pumpNumber(bar()), 5);
-assert.strictEqual(pumpNumber(foo()), 10);
diff --git a/test/fixtures/transformation/es6-generators/yield-star-expression-results-have-correct-values/exec.js b/test/fixtures/transformation/es6-generators/yield-star-expression-results-have-correct-values/exec.js
deleted file mode 100644
index 8622122707..0000000000
--- a/test/fixtures/transformation/es6-generators/yield-star-expression-results-have-correct-values/exec.js
+++ /dev/null
@@ -1,11 +0,0 @@
-function* foo() {
-  yield 0;
-  return yield* bar();
-}
-
-function* bar() {
-  yield 1;
-  return 2;
-}
-
-genHelpers.check(foo(), [0, 1], 2);
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/closure/actual.js b/test/fixtures/transformation/es6-let-scoping-traceur/closure/actual.js
deleted file mode 100644
index e443b2633f..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/closure/actual.js
+++ /dev/null
@@ -1,9 +0,0 @@
-(function() {
-  let foo = 'bar';
-
-  [true].forEach(function() {
-    foo = 'baz';
-  });
-
-  console.log(foo);
-});
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/closure/expected.js b/test/fixtures/transformation/es6-let-scoping-traceur/closure/expected.js
deleted file mode 100644
index ae5ea97d75..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/closure/expected.js
+++ /dev/null
@@ -1,11 +0,0 @@
-"use strict";
-
-(function () {
-  var foo = "bar";
-
-  [true].forEach(function () {
-    foo = "baz";
-  });
-
-  console.log(foo);
-});
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/deep-nested/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/deep-nested/exec.js
deleted file mode 100644
index 6880f64525..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/deep-nested/exec.js
+++ /dev/null
@@ -1,9 +0,0 @@
-var a = 'var a';
-{
-  var b = 'var b';
-  {
-    var c = 'var c';
-    let d = 'let d';
-    assert.equal(d, 'let d');
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/for-in-initializers/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/for-in-initializers/exec.js
deleted file mode 100644
index 3228d3680e..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/for-in-initializers/exec.js
+++ /dev/null
@@ -1,17 +0,0 @@
-var result;
-{
-  let let_result = [];
-  let let_array = ['one', 'two', 'three'];
-  for (var index in let_array) {
-    let let_index = index;
-    let let_value = let_array[let_index];
-    let_result.push(function () {
-      return [let_index, let_value];
-    });
-  }
-  result = let_result;
-}
-
-assert.deepEqual(['0', 'one'], result[0]());
-assert.deepEqual(['1', 'two'], result[1]());
-assert.deepEqual(['2', 'three'], result[2]());
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/for-initializers/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/for-initializers/exec.js
deleted file mode 100644
index 89892cb5c3..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/for-initializers/exec.js
+++ /dev/null
@@ -1,26 +0,0 @@
-var result;
-{
-  let let_x = 'let x';
-  let let_l = [];
-  for (var var_x = 1, var_y = 2, var_z = 3; var_x < 10; var_x ++) {
-    let l_x = var_x, l_y = var_y, l_z = var_z;
-    let_l.push(function () {
-      return [l_x, l_y, l_z];
-    });
-  }
-  result = let_l;
-}
-
-assert.deepEqual(result.map(function (fn) {
-  return fn();
-}), [
-  [ 1, 2, 3 ],
-  [ 2, 2, 3 ],
-  [ 3, 2, 3 ],
-  [ 4, 2, 3 ],
-  [ 5, 2, 3 ],
-  [ 6, 2, 3 ],
-  [ 7, 2, 3 ],
-  [ 8, 2, 3 ],
-  [ 9, 2, 3 ]
-]);
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/function-declaration/actual.js b/test/fixtures/transformation/es6-let-scoping-traceur/function-declaration/actual.js
deleted file mode 100644
index fdd92c1221..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/function-declaration/actual.js
+++ /dev/null
@@ -1,9 +0,0 @@
-domready(function () {
-  let a = 1;
-  const b = 1;
-  runIt();
-
-  function runIt() {
-    console.log(a + b);
-  }
-});
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/function-declaration/expected.js b/test/fixtures/transformation/es6-let-scoping-traceur/function-declaration/expected.js
deleted file mode 100644
index 3e681cb35b..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/function-declaration/expected.js
+++ /dev/null
@@ -1,11 +0,0 @@
-"use strict";
-
-domready(function () {
-  var a = 1;
-  var b = 1;
-  runIt();
-
-  function runIt() {
-    console.log(a + b);
-  }
-});
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-class/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-class/exec.js
deleted file mode 100644
index d410cf0ccb..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-class/exec.js
+++ /dev/null
@@ -1,15 +0,0 @@
-class LetInClass {
-  get z() {
-  let let_z = 10;
-  return let_z;
-  }
-
-  set z(v) {
-  let let_zv = v;
-  }
-
-  distance() {
-  let dist = this.y - this.x;
-  return dist;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-closure/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-closure/exec.js
deleted file mode 100644
index e01538c804..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-closure/exec.js
+++ /dev/null
@@ -1,21 +0,0 @@
-function letInClosure(n) {
-  var l = [];
-  for (var i = 0; i < n; i ++) {
-    let let_i = i;
-    if (i % 3 == 0) {
-      continue;
-    }
-    l.push(function () {
-      return let_i;
-    });
-  }
-  return l;
-}
-
-var result = letInClosure(10);
-assert.equal(1, result[0]());
-assert.equal(2, result[1]());
-assert.equal(4, result[2]());
-assert.equal(5, result[3]());
-assert.equal(7, result[4]());
-assert.equal(8, result[5]());
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break-inner/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break-inner/exec.js
deleted file mode 100644
index 802fed4059..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break-inner/exec.js
+++ /dev/null
@@ -1,8 +0,0 @@
-for (var x = 0; x < 10; x ++) {
-  for (var y = 0; y < 10; y ++) {
-  let z = 'let z';
-  if (x == 7) {
-    break;
-  }
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break-named/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break-named/exec.js
deleted file mode 100644
index 973ea8e35f..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break-named/exec.js
+++ /dev/null
@@ -1,9 +0,0 @@
-outer:
-for (var x = 0; x < 10; x ++) {
-  for (var y = 0; y < 10; y ++) {
-  let z = 'let z';
-  if (x == 7) {
-    break outer;
-  }
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break/exec.js
deleted file mode 100644
index 1fbe54486d..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-break/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-for (var x = 0; x < 10; x ++) {
-  let y = 'let y';
-  if (x % 2 == 0) {
-  break;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue-inner/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue-inner/exec.js
deleted file mode 100644
index 539d540e3a..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue-inner/exec.js
+++ /dev/null
@@ -1,8 +0,0 @@
-for (var x = 0; x < 10; x ++) {
-  for (var y = 0; y < 10; y ++) {
-  let z = 'let z';
-  if (x == 7) {
-    continue;
-  }
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue-named/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue-named/exec.js
deleted file mode 100644
index 85efb6541d..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue-named/exec.js
+++ /dev/null
@@ -1,9 +0,0 @@
-outer:
-for (var x = 0; x < 10; x ++) {
-  for (var y = 0; y < 10; y ++) {
-  let z = 'let z';
-  if (x == 7) {
-    continue outer;
-  }
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue/exec.js
deleted file mode 100644
index 4458457d71..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for-continue/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-for (var x = 0; x < 10; x ++) {
-  let y = 'let y';
-  if (x % 2 == 0) {
-  continue;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-for/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-for/exec.js
deleted file mode 100644
index de1630e09e..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-for/exec.js
+++ /dev/null
@@ -1,3 +0,0 @@
-for (var x = 0; x < 10; x ++) {
-  let y = 'let y';
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/in-properties/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/in-properties/exec.js
deleted file mode 100644
index 9cba2236c1..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/in-properties/exec.js
+++ /dev/null
@@ -1,15 +0,0 @@
-var object = {
-  get x() {
-    while (true) {
-      let let_x = 'let x';
-      return let_x;
-    }
-  },
-
-  set x(v) {
-    do {
-      let let_v = v;
-      this.v = let_v;
-    } while (false);
-  }
-};
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-1/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-1/exec.js
deleted file mode 100644
index dd2909dea2..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-1/exec.js
+++ /dev/null
@@ -1,3 +0,0 @@
-for (let x = 1; x < 10; x++) {
-  x;
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-2/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-2/exec.js
deleted file mode 100644
index a2bd89dbac..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-2/exec.js
+++ /dev/null
@@ -1,4 +0,0 @@
-for (let x = 1, y = 2, z = 3; x < 10; x ++) {
-  y++;
-  z++;
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-3/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-3/exec.js
deleted file mode 100644
index 73f4794698..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-3/exec.js
+++ /dev/null
@@ -1,5 +0,0 @@
-for (let x = 1, y = x + 1; x < 10 && y != 0; x ++, y *= 2) {
-  if (y > 300) {
-  continue;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-in/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-in/exec.js
deleted file mode 100644
index b80574713d..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/initializer-for-in/exec.js
+++ /dev/null
@@ -1,5 +0,0 @@
-let sum = 0;
-let a = [1,2,3];
-for (let x in a) {
-  sum = sum + a[x];
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/nested-conflict/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/nested-conflict/exec.js
deleted file mode 100644
index 4243019c5f..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/nested-conflict/exec.js
+++ /dev/null
@@ -1,12 +0,0 @@
-(function () {
-  var x = 1;
-  function f() {
-  assert.equal(x, 1);
-  {
-    let x = 2;
-    assert.equal(x, 2);
-  }
-  assert.equal(x, 1);
-  }
-  f();
-})();
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-1/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-1/exec.js
deleted file mode 100644
index 617db23c44..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-1/exec.js
+++ /dev/null
@@ -1,5 +0,0 @@
-function nestedFunction1() {
-  return function () {
-  let let_x = 'let x';
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-2/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-2/exec.js
deleted file mode 100644
index f993f344c2..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-2/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-function nestedFunction2() {
-  let let_func = function () {
-  let let_x = 'let x';
-  }
-  return let_func;
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-3/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-3/exec.js
deleted file mode 100644
index 3e45d93ff5..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/nested-function-3/exec.js
+++ /dev/null
@@ -1,4 +0,0 @@
-function nestedFunction3() {
-  let let_x = 'let x';
-  function function_foo() { }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/nested/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/nested/exec.js
deleted file mode 100644
index bf9b8f57d0..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/nested/exec.js
+++ /dev/null
@@ -1,7 +0,0 @@
-var x = 'var';
-{
-  let y = 'let 1';
-}
-{
-  let y = 'let 2';
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/no-initializer-global/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/no-initializer-global/exec.js
deleted file mode 100644
index f01f21783d..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/no-initializer-global/exec.js
+++ /dev/null
@@ -1,4 +0,0 @@
-let x2;
-assert.equal(undefined, x2);
-x2 = 2;
-assert.equal(2, x2);
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/no-initializer/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/no-initializer/exec.js
deleted file mode 100644
index f9d28fb681..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/no-initializer/exec.js
+++ /dev/null
@@ -1,8 +0,0 @@
-var x = 1;
-{
-  let x;
-  assert.equal(undefined, x);
-  x = 2;
-  assert.equal(2, x);
-}
-assert.equal(1, x);
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/no-renaming/actual.js b/test/fixtures/transformation/es6-let-scoping-traceur/no-renaming/actual.js
deleted file mode 100644
index c26fd3ff99..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/no-renaming/actual.js
+++ /dev/null
@@ -1,6 +0,0 @@
-function foo (n) {
-  let bar = n;
-  eval('console.log(bar)');
-}
-
-foo(42);
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/no-renaming/expected.js b/test/fixtures/transformation/es6-let-scoping-traceur/no-renaming/expected.js
deleted file mode 100644
index 5499842172..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/no-renaming/expected.js
+++ /dev/null
@@ -1,8 +0,0 @@
-"use strict";
-
-function foo(n) {
-  var bar = n;
-  eval("console.log(bar)");
-}
-
-foo(42);
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/regress-1381/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/regress-1381/exec.js
deleted file mode 100644
index 26c224809a..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/regress-1381/exec.js
+++ /dev/null
@@ -1,8 +0,0 @@
-function test() {
-  let ret = true;
-  while (false)
-  for (let i = 0; i < 1; i++)
-    ret = () => i;
-  return ret
-}
-assert.ok(test());
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/with-for-in/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/with-for-in/exec.js
deleted file mode 100644
index 7f6fbf1740..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/with-for-in/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-for (var x in [1,2,3]) {
-  let let_y = x;
-  for (var for_in_z in [4,5,6]) {
-  continue;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/with-for/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/with-for/exec.js
deleted file mode 100644
index 07912563f8..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/with-for/exec.js
+++ /dev/null
@@ -1,6 +0,0 @@
-for (var x = 0; x < 10; x++) {
-  let let_y = 'let y';
-  for (var for_z = 0; for_z < 2; for_z ++) {
-  break;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping-traceur/with-switch/exec.js b/test/fixtures/transformation/es6-let-scoping-traceur/with-switch/exec.js
deleted file mode 100644
index 5100a8032e..0000000000
--- a/test/fixtures/transformation/es6-let-scoping-traceur/with-switch/exec.js
+++ /dev/null
@@ -1,12 +0,0 @@
-for (var i = 0; i < 5; i ++) {
-  let let_x = 'let x';
-
-  switch (i) {
-  case 0:
-    break;
-  case 2:
-    break;
-  default:
-    break;
-  }
-}
diff --git a/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/actual.js b/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/actual.js
index 387d702154..cb38abee39 100644
--- a/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/actual.js
+++ b/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/actual.js
@@ -1,10 +1,12 @@
-for (let i in nums) {
-  fns.push(function () { return i; });
-  if (i === 1) {
-    continue;
-  } else if (i === 2) {
-    break;
-  } else if (i === 3) {
-    return i;
+(function () {
+  for (let i in nums) {
+    fns.push(function () { return i; });
+    if (i === 1) {
+      continue;
+    } else if (i === 2) {
+      break;
+    } else if (i === 3) {
+      return i;
+    }
   }
-}
+})();
diff --git a/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/expected.js b/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/expected.js
index ff74908db9..29f844e7d1 100644
--- a/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/expected.js
+++ b/test/fixtures/transformation/es6-let-scoping/for-break-continue-return/expected.js
@@ -1,27 +1,29 @@
 "use strict";
 
-_loop: for (var i in nums) {
-  var _ret = (function (i) {
-    fns.push(function () {
-      return i;
-    });
-    if (i === 1) {
-      return "continue";
-    } else if (i === 2) {
-      return "break";
-    } else if (i === 3) {
-      return {
-        v: i
-      };
-    }
-  })(i);
+(function () {
+  _loop: for (var i in nums) {
+    var _ret = (function (i) {
+      fns.push(function () {
+        return i;
+      });
+      if (i === 1) {
+        return "continue";
+      } else if (i === 2) {
+        return "break";
+      } else if (i === 3) {
+        return {
+          v: i
+        };
+      }
+    })(i);
 
-  switch (_ret) {
-    case "break":
-      break _loop;
-    case "continue":
-      continue _loop;
-    default:
-      if (typeof _ret === "object") return _ret.v;
+    switch (_ret) {
+      case "break":
+        break _loop;
+      case "continue":
+        continue _loop;
+      default:
+        if (typeof _ret === "object") return _ret.v;
+    }
   }
-}
+})();
diff --git a/test/fixtures/transformation/es6-let-scoping/for-return-undefined/actual.js b/test/fixtures/transformation/es6-let-scoping/for-return-undefined/actual.js
index b7613b4f31..526485919b 100644
--- a/test/fixtures/transformation/es6-let-scoping/for-return-undefined/actual.js
+++ b/test/fixtures/transformation/es6-let-scoping/for-return-undefined/actual.js
@@ -1,4 +1,6 @@
-for (let i in nums) {
-  fns.push(function () { return i; });
-  return;
-}
+(function () {
+  for (let i in nums) {
+    fns.push(function () { return i; });
+    return;
+  }
+})();
diff --git a/test/fixtures/transformation/es6-let-scoping/for-return-undefined/expected.js b/test/fixtures/transformation/es6-let-scoping/for-return-undefined/expected.js
index 4937ff43c2..6fb72fe444 100644
--- a/test/fixtures/transformation/es6-let-scoping/for-return-undefined/expected.js
+++ b/test/fixtures/transformation/es6-let-scoping/for-return-undefined/expected.js
@@ -1,14 +1,16 @@
 "use strict";
 
-for (var i in nums) {
-  var _ret = (function (i) {
-    fns.push(function () {
-      return i;
-    });
-    return {
-      v: undefined
-    };
-  })(i);
+(function () {
+  for (var i in nums) {
+    var _ret = (function (i) {
+      fns.push(function () {
+        return i;
+      });
+      return {
+        v: undefined
+      };
+    })(i);
 
-  if (typeof _ret === "object") return _ret.v;
-}
+    if (typeof _ret === "object") return _ret.v;
+  }
+})();
diff --git a/test/fixtures/transformation/es6-let-scoping/for-return/actual.js b/test/fixtures/transformation/es6-let-scoping/for-return/actual.js
index 8c636baaca..339cdd507f 100644
--- a/test/fixtures/transformation/es6-let-scoping/for-return/actual.js
+++ b/test/fixtures/transformation/es6-let-scoping/for-return/actual.js
@@ -1,4 +1,6 @@
-for (let i in nums) {
-  fns.push(function () { return i; });
-  return i;
-}
+(function () {
+  for (let i in nums) {
+    fns.push(function () { return i; });
+    return i;
+  }
+})();
diff --git a/test/fixtures/transformation/es6-let-scoping/for-return/expected.js b/test/fixtures/transformation/es6-let-scoping/for-return/expected.js
index d26f70a201..fa088e1c12 100644
--- a/test/fixtures/transformation/es6-let-scoping/for-return/expected.js
+++ b/test/fixtures/transformation/es6-let-scoping/for-return/expected.js
@@ -1,14 +1,16 @@
 "use strict";
 
-for (var i in nums) {
-  var _ret = (function (i) {
-    fns.push(function () {
-      return i;
-    });
-    return {
-      v: i
-    };
-  })(i);
+(function () {
+  for (var i in nums) {
+    var _ret = (function (i) {
+      fns.push(function () {
+        return i;
+      });
+      return {
+        v: i
+      };
+    })(i);
 
-  if (typeof _ret === "object") return _ret.v;
-}
+    if (typeof _ret === "object") return _ret.v;
+  }
+})();
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-default/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-default/expected.js
index cd75b3299d..a97787be5e 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-default/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-default/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports", "module"], function (exports, module) {
+  "use strict";
+
   module.exports = foo;
   module.exports = 42;
   module.exports = {};
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js
index 8e2d46f06e..0ff3782345 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-from/expected.js
@@ -1,11 +1,21 @@
-"use strict";
-
 define(["exports", "foo"], function (exports, _foo) {
-  (function (obj) {
+  "use strict";
+
+  var _interopRequireWildcard = function (obj) {
+    return obj && obj.constructor === Object ? obj : {
+      "default": obj
+    };
+  };
+
+  var _exportsWildcard = function (obj) {
     for (var i in obj) {
-      exports[i] = obj[i];
+      if (exports[i] !== undefined) {
+        exports[i] = obj[i];
+      }
     }
-  })(_foo);
+  };
+
+  _exportsWildcard(_interopRequireWildcard(_foo));
 
   exports.foo = _foo.foo;
   exports.foo = _foo.foo;
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js
index b0b1105638..76c505a7ce 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-named/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports"], function (exports) {
+  "use strict";
+
   exports.foo = foo;
   exports.foo = foo;
   exports.bar = bar;
@@ -8,4 +8,4 @@ define(["exports"], function (exports) {
   exports["default"] = foo;
   exports["default"] = foo;
   exports.bar = bar;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js
index fb8d31ad7e..f31d875c89 100644
--- a/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/exports-variable/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports"], function (exports) {
+  "use strict";
+
   exports.foo7 = foo7;
   var foo = exports.foo = 1;
   var foo = exports.foo = 1;
@@ -14,4 +14,4 @@ define(["exports"], function (exports) {
   var foo8 = function foo8() {};
 
   exports.foo8 = foo8;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js
index 666b374c65..5f8f8e9886 100644
--- a/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/hoist-function-exports/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports", "./evens"], function (exports, _evens) {
+  "use strict";
+
   exports.nextOdd = nextOdd;
   var isEven = _evens.isEven;
   function nextOdd(n) {
@@ -12,4 +12,4 @@ define(["exports", "./evens"], function (exports, _evens) {
       return !isEven(n);
     };
   })(isEven);
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/imports-default/expected.js b/test/fixtures/transformation/es6-modules-amd/imports-default/expected.js
index 84f49c3f1f..78a5151d3a 100644
--- a/test/fixtures/transformation/es6-modules-amd/imports-default/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/imports-default/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports", "foo"], function (exports, _foo) {
+  "use strict";
+
   var _interopRequire = function (obj) {
     return obj && (obj["default"] || obj);
   };
@@ -8,4 +8,4 @@ define(["exports", "foo"], function (exports, _foo) {
   var foo = _interopRequire(_foo);
 
   var foo = _interopRequire(_foo);
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/imports-glob/expected.js b/test/fixtures/transformation/es6-modules-amd/imports-glob/expected.js
index 414d126b14..cc03946787 100644
--- a/test/fixtures/transformation/es6-modules-amd/imports-glob/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/imports-glob/expected.js
@@ -1,5 +1,5 @@
-"use strict";
-
 define(["exports", "foo"], function (exports, _foo) {
+  "use strict";
+
   var foo = _foo;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/imports-mixing/expected.js b/test/fixtures/transformation/es6-modules-amd/imports-mixing/expected.js
index 406cfab22b..8acd23bf34 100644
--- a/test/fixtures/transformation/es6-modules-amd/imports-mixing/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/imports-mixing/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports", "foo"], function (exports, _foo) {
+  "use strict";
+
   var _interopRequire = function (obj) {
     return obj && (obj["default"] || obj);
   };
@@ -8,4 +8,4 @@ define(["exports", "foo"], function (exports, _foo) {
   var foo = _interopRequire(_foo);
 
   var xyz = _foo.baz;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/imports-named/expected.js b/test/fixtures/transformation/es6-modules-amd/imports-named/expected.js
index 8912d46bae..5140508011 100644
--- a/test/fixtures/transformation/es6-modules-amd/imports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/imports-named/expected.js
@@ -1,10 +1,10 @@
-"use strict";
-
 define(["exports", "foo"], function (exports, _foo) {
+  "use strict";
+
   var bar = _foo.bar;
   var bar = _foo.bar;
   var baz = _foo.baz;
   var baz = _foo.bar;
   var baz = _foo.bar;
   var xyz = _foo.xyz;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/imports/expected.js b/test/fixtures/transformation/es6-modules-amd/imports/expected.js
index d3f30c8b16..84e1e6dcc7 100644
--- a/test/fixtures/transformation/es6-modules-amd/imports/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/imports/expected.js
@@ -1,3 +1,3 @@
-"use strict";
-
-define(["exports", "foo", "foo-bar", "./directory/foo-bar"], function (exports, _foo, _fooBar, _directoryFooBar) {});
+define(["exports", "foo", "foo-bar", "./directory/foo-bar"], function (exports, _foo, _fooBar, _directoryFooBar) {
+  "use strict";
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/module-name/expected.js b/test/fixtures/transformation/es6-modules-amd/module-name/expected.js
index 9b7a5fee64..c129a9ffb6 100644
--- a/test/fixtures/transformation/es6-modules-amd/module-name/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/module-name/expected.js
@@ -1,5 +1,5 @@
-"use strict";
-
 define("es6-modules-amd/module-name/expected", ["exports"], function (exports) {
+  "use strict";
+
   foobar();
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-amd/overview/expected.js b/test/fixtures/transformation/es6-modules-amd/overview/expected.js
index ed099200aa..d1c203ae88 100644
--- a/test/fixtures/transformation/es6-modules-amd/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/overview/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports", "module", "foo", "foo-bar", "./directory/foo-bar"], function (exports, module, _foo, _fooBar, _directoryFooBar) {
+  "use strict";
+
   var _interopRequire = function (obj) {
     return obj && (obj["default"] || obj);
   };
diff --git a/test/fixtures/transformation/es6-modules-amd/remap/expected.js b/test/fixtures/transformation/es6-modules-amd/remap/expected.js
index 9d30a0f7bd..1edd3204c1 100644
--- a/test/fixtures/transformation/es6-modules-amd/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-amd/remap/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 define(["exports"], function (exports) {
+  "use strict";
+
   var test = exports.test = 2;
   test = exports.test = 5;
   test = exports.test += 1;
@@ -10,4 +10,4 @@ define(["exports"], function (exports) {
     test = 3;
     test++;
   })();
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-common/exports-from/expected.js b/test/fixtures/transformation/es6-modules-common/exports-from/expected.js
index feaeac94ee..2264dd7c1a 100644
--- a/test/fixtures/transformation/es6-modules-common/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/exports-from/expected.js
@@ -1,10 +1,20 @@
 "use strict";
 
-(function (obj) {
+var _interopRequireWildcard = function (obj) {
+  return obj && obj.constructor === Object ? obj : {
+    "default": obj
+  };
+};
+
+var _exportsWildcard = function (obj) {
   for (var i in obj) {
-    exports[i] = obj[i];
+    if (exports[i] !== undefined) {
+      exports[i] = obj[i];
+    }
   }
-})(require("foo"));
+};
+
+_exportsWildcard(_interopRequireWildcard(require("foo")));
 
 exports.foo = require("foo").foo;
 exports.foo = require("foo").foo;
diff --git a/test/fixtures/transformation/es6-modules-common/imports-glob/expected.js b/test/fixtures/transformation/es6-modules-common/imports-glob/expected.js
index 3293bd0ebd..d885f06222 100644
--- a/test/fixtures/transformation/es6-modules-common/imports-glob/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/imports-glob/expected.js
@@ -1,3 +1,9 @@
 "use strict";
 
-var foo = require("foo");
+var _interopRequireWildcard = function (obj) {
+  return obj && obj.constructor === Object ? obj : {
+    "default": obj
+  };
+};
+
+var foo = _interopRequireWildcard(require("foo"));
diff --git a/test/fixtures/transformation/es6-modules-common/overview/expected.js b/test/fixtures/transformation/es6-modules-common/overview/expected.js
index ed9175cbfb..9ce11f0b0d 100644
--- a/test/fixtures/transformation/es6-modules-common/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-common/overview/expected.js
@@ -1,5 +1,11 @@
 "use strict";
 
+var _interopRequireWildcard = function (obj) {
+  return obj && obj.constructor === Object ? obj : {
+    "default": obj
+  };
+};
+
 var _interopRequire = function (obj) {
   return obj && (obj["default"] || obj);
 };
@@ -12,7 +18,7 @@ require("./directory/foo-bar");
 
 var foo = _interopRequire(require("foo"));
 
-var foo = require("foo");
+var foo = _interopRequireWildcard(require("foo"));
 
 var bar = require("foo").bar;
 var bar = require("foo").foo;
diff --git a/test/fixtures/transformation/es6-modules-system/exports-default/expected.js b/test/fixtures/transformation/es6-modules-system/exports-default/expected.js
index 8761dda421..bf1e155301 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-default/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-default/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register([], function (_export) {
+  "use strict";
+
   var Foo;
   _export("default", foo);
 
@@ -25,4 +25,4 @@ System.register([], function (_export) {
       _export("default", Foo);
     }
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/exports-from/expected.js b/test/fixtures/transformation/es6-modules-system/exports-from/expected.js
index 00bbddc855..7f9a382a09 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-from/expected.js
@@ -1,10 +1,10 @@
-"use strict";
-
 System.register(["foo"], function (_export) {
+  "use strict";
+
   return {
     setters: [function (_foo) {
       for (var _key in _foo) {
-        _export(_key, _foo[_key])
+        _export(_key, _foo[_key]);
       }
 
       _export("foo", _foo.foo);
@@ -23,4 +23,4 @@ System.register(["foo"], function (_export) {
     }],
     execute: function () {}
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/exports-named/expected.js b/test/fixtures/transformation/es6-modules-system/exports-named/expected.js
index 2f06c0c7d6..195854646f 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-named/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register([], function (_export) {
+  "use strict";
+
   return {
     setters: [],
     execute: function () {
@@ -19,4 +19,4 @@ System.register([], function (_export) {
       _export("bar", bar);
     }
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js
index 0d8c870385..9c643cfdb6 100644
--- a/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/exports-variable/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register([], function (_export) {
+  "use strict";
+
   var foo, foo2, foo3, foo4, foo5, foo6, foo8;
   _export("foo7", foo7);
 
@@ -19,4 +19,4 @@ System.register([], function (_export) {
       _export("foo8", foo8);
     }
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js
index 53451797b2..a5aae84ee7 100644
--- a/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/hoist-function-exports/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register(["./evens"], function (_export) {
+  "use strict";
+
   var isEven, p, isOdd;
   _export("nextOdd", nextOdd);
 
@@ -21,4 +21,4 @@ System.register(["./evens"], function (_export) {
       })(isEven));
     }
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/imports-default/expected.js b/test/fixtures/transformation/es6-modules-system/imports-default/expected.js
index 6398509e9e..8164489973 100644
--- a/test/fixtures/transformation/es6-modules-system/imports-default/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/imports-default/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var foo, foo;
   return {
     setters: [function (_foo) {
@@ -9,4 +9,4 @@ System.register(["foo"], function (_export) {
     }],
     execute: function () {}
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/imports-glob/expected.js b/test/fixtures/transformation/es6-modules-system/imports-glob/expected.js
index d2176e441c..6e08c8dcc9 100644
--- a/test/fixtures/transformation/es6-modules-system/imports-glob/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/imports-glob/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var foo;
   return {
     setters: [function (_foo) {
@@ -8,4 +8,4 @@ System.register(["foo"], function (_export) {
     }],
     execute: function () {}
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/imports-mixing/expected.js b/test/fixtures/transformation/es6-modules-system/imports-mixing/expected.js
index c3f67fcf72..31b6f179ea 100644
--- a/test/fixtures/transformation/es6-modules-system/imports-mixing/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/imports-mixing/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var foo, xyz;
   return {
     setters: [function (_foo) {
@@ -9,4 +9,4 @@ System.register(["foo"], function (_export) {
     }],
     execute: function () {}
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/imports-named/expected.js b/test/fixtures/transformation/es6-modules-system/imports-named/expected.js
index ead590f0a5..848c4a28ba 100644
--- a/test/fixtures/transformation/es6-modules-system/imports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/imports-named/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register(["foo"], function (_export) {
+  "use strict";
+
   var bar, bar, baz, baz, baz, xyz;
   return {
     setters: [function (_foo) {
@@ -13,4 +13,4 @@ System.register(["foo"], function (_export) {
     }],
     execute: function () {}
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/imports/expected.js b/test/fixtures/transformation/es6-modules-system/imports/expected.js
index d976b200ce..595df89e93 100644
--- a/test/fixtures/transformation/es6-modules-system/imports/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/imports/expected.js
@@ -1,8 +1,8 @@
-"use strict";
-
 System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
+  "use strict";
+
   return {
     setters: [function (_foo) {}, function (_fooBar) {}, function (_directoryFooBar) {}],
     execute: function () {}
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/overview/expected.js b/test/fixtures/transformation/es6-modules-system/overview/expected.js
index e0e40a9fda..59e6c96af2 100644
--- a/test/fixtures/transformation/es6-modules-system/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/overview/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
+  "use strict";
+
   var foo, foo, bar, bar, test;
   return {
     setters: [function (_foo) {
@@ -16,4 +16,4 @@ System.register(["foo", "foo-bar", "./directory/foo-bar"], function (_export) {
       _export("default", test);
     }
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-system/remap/expected.js b/test/fixtures/transformation/es6-modules-system/remap/expected.js
index 015a3b3c76..446bdfcc9a 100644
--- a/test/fixtures/transformation/es6-modules-system/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-system/remap/expected.js
@@ -1,6 +1,6 @@
-"use strict";
-
 System.register([], function (_export) {
+  "use strict";
+
   var test;
   return {
     setters: [],
@@ -16,4 +16,4 @@ System.register([], function (_export) {
       })();
     }
   };
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-default/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-default/expected.js
index f61ef367a2..384b5e8f43 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-default/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-default/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "module"], factory);
@@ -7,6 +5,8 @@
     factory(exports, module);
   }
 })(function (exports, module) {
+  "use strict";
+
   module.exports = foo;
   module.exports = 42;
   module.exports = {};
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-default/untitled b/test/fixtures/transformation/es6-modules-umd/exports-default/untitled
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js
index 522d97be92..2f84be3a91 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-from/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "foo"], factory);
@@ -7,11 +5,23 @@
     factory(exports, require("foo"));
   }
 })(function (exports, _foo) {
-  (function (obj) {
+  "use strict";
+
+  var _interopRequireWildcard = function (obj) {
+    return obj && obj.constructor === Object ? obj : {
+      "default": obj
+    };
+  };
+
+  var _exportsWildcard = function (obj) {
     for (var i in obj) {
-      exports[i] = obj[i];
+      if (exports[i] !== undefined) {
+        exports[i] = obj[i];
+      }
     }
-  })(_foo);
+  };
+
+  _exportsWildcard(_interopRequireWildcard(_foo));
 
   exports.foo = _foo.foo;
   exports.foo = _foo.foo;
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js
index ca8dc8d3c5..bb59a54207 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-named/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports"], factory);
@@ -7,6 +5,8 @@
     factory(exports);
   }
 })(function (exports) {
+  "use strict";
+
   exports.foo = foo;
   exports.foo = foo;
   exports.bar = bar;
@@ -14,4 +14,4 @@
   exports["default"] = foo;
   exports["default"] = foo;
   exports.bar = bar;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js b/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js
index 9fa63e55f1..f8011621be 100644
--- a/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/exports-variable/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports"], factory);
@@ -7,6 +5,8 @@
     factory(exports);
   }
 })(function (exports) {
+  "use strict";
+
   exports.foo7 = foo7;
   var foo = exports.foo = 1;
   var foo = exports.foo = 1;
@@ -20,4 +20,4 @@
   var foo8 = function foo8() {};
 
   exports.foo8 = foo8;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js b/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js
index bced4aee50..e2ec28a22c 100644
--- a/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/hoist-function-exports/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "./evens"], factory);
@@ -7,6 +5,8 @@
     factory(exports, require("./evens"));
   }
 })(function (exports, _evens) {
+  "use strict";
+
   exports.nextOdd = nextOdd;
   var isEven = _evens.isEven;
   function nextOdd(n) {
@@ -18,4 +18,4 @@
       return !isEven(n);
     };
   })(isEven);
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/imports-default/expected.js b/test/fixtures/transformation/es6-modules-umd/imports-default/expected.js
index aecbf9e589..f68f912f15 100644
--- a/test/fixtures/transformation/es6-modules-umd/imports-default/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/imports-default/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "foo"], factory);
@@ -7,6 +5,8 @@
     factory(exports, require("foo"));
   }
 })(function (exports, _foo) {
+  "use strict";
+
   var _interopRequire = function (obj) {
     return obj && (obj["default"] || obj);
   };
@@ -14,4 +14,4 @@
   var foo = _interopRequire(_foo);
 
   var foo = _interopRequire(_foo);
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/imports-glob/expected.js b/test/fixtures/transformation/es6-modules-umd/imports-glob/expected.js
index 7dc4aeb30a..45a763f2f2 100644
--- a/test/fixtures/transformation/es6-modules-umd/imports-glob/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/imports-glob/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "foo"], factory);
@@ -7,5 +5,7 @@
     factory(exports, require("foo"));
   }
 })(function (exports, _foo) {
+  "use strict";
+
   var foo = _foo;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/imports-mixing/expected.js b/test/fixtures/transformation/es6-modules-umd/imports-mixing/expected.js
index 6ab5bdd395..f677ceee86 100644
--- a/test/fixtures/transformation/es6-modules-umd/imports-mixing/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/imports-mixing/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "foo"], factory);
@@ -7,6 +5,8 @@
     factory(exports, require("foo"));
   }
 })(function (exports, _foo) {
+  "use strict";
+
   var _interopRequire = function (obj) {
     return obj && (obj["default"] || obj);
   };
@@ -14,4 +14,4 @@
   var foo = _interopRequire(_foo);
 
   var xyz = _foo.baz;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/imports-named/expected.js b/test/fixtures/transformation/es6-modules-umd/imports-named/expected.js
index 896105f29c..2d75892bf6 100644
--- a/test/fixtures/transformation/es6-modules-umd/imports-named/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/imports-named/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "foo"], factory);
@@ -7,10 +5,12 @@
     factory(exports, require("foo"));
   }
 })(function (exports, _foo) {
+  "use strict";
+
   var bar = _foo.bar;
   var bar = _foo.bar;
   var baz = _foo.baz;
   var baz = _foo.bar;
   var baz = _foo.bar;
   var xyz = _foo.xyz;
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/imports/expected.js b/test/fixtures/transformation/es6-modules-umd/imports/expected.js
index abcaf5b99a..2e39b15cd2 100644
--- a/test/fixtures/transformation/es6-modules-umd/imports/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/imports/expected.js
@@ -1,9 +1,9 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "foo", "foo-bar", "./directory/foo-bar"], factory);
   } else if (typeof exports !== "undefined") {
     factory(exports, require("foo"), require("foo-bar"), require("./directory/foo-bar"));
   }
-})(function (exports, _foo, _fooBar, _directoryFooBar) {});
+})(function (exports, _foo, _fooBar, _directoryFooBar) {
+  "use strict";
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/module-name/expected.js b/test/fixtures/transformation/es6-modules-umd/module-name/expected.js
index 73834cdd3b..aa570b25e3 100644
--- a/test/fixtures/transformation/es6-modules-umd/module-name/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/module-name/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define("es6-modules-umd/module-name/expected", ["exports"], factory);
@@ -7,5 +5,7 @@
     factory(exports);
   }
 })(function (exports) {
+  "use strict";
+
   foobar();
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-modules-umd/overview/expected.js b/test/fixtures/transformation/es6-modules-umd/overview/expected.js
index 594322dac5..73f835715e 100644
--- a/test/fixtures/transformation/es6-modules-umd/overview/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/overview/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports", "module", "foo", "foo-bar", "./directory/foo-bar"], factory);
@@ -7,6 +5,8 @@
     factory(exports, module, require("foo"), require("foo-bar"), require("./directory/foo-bar"));
   }
 })(function (exports, module, _foo, _fooBar, _directoryFooBar) {
+  "use strict";
+
   var _interopRequire = function (obj) {
     return obj && (obj["default"] || obj);
   };
diff --git a/test/fixtures/transformation/es6-modules-umd/remap/expected.js b/test/fixtures/transformation/es6-modules-umd/remap/expected.js
index 679d11511f..99e5928e2d 100644
--- a/test/fixtures/transformation/es6-modules-umd/remap/expected.js
+++ b/test/fixtures/transformation/es6-modules-umd/remap/expected.js
@@ -1,5 +1,3 @@
-"use strict";
-
 (function (factory) {
   if (typeof define === "function" && define.amd) {
     define(["exports"], factory);
@@ -7,6 +5,8 @@
     factory(exports);
   }
 })(function (exports) {
+  "use strict";
+
   var test = exports.test = 2;
   test = exports.test = 5;
   test = exports.test += 1;
@@ -16,4 +16,4 @@
     test = 3;
     test++;
   })();
-});
+});
\ No newline at end of file
diff --git a/test/fixtures/transformation/es6-rest-parameters/arrow-functions/expected.js b/test/fixtures/transformation/es6-rest-parameters/arrow-functions/expected.js
index 49c1d11e53..cb971ebc77 100644
--- a/test/fixtures/transformation/es6-rest-parameters/arrow-functions/expected.js
+++ b/test/fixtures/transformation/es6-rest-parameters/arrow-functions/expected.js
@@ -1,6 +1,9 @@
 "use strict";
 
-var _slice = Array.prototype.slice;
 var concat = function () {
-  var arrs = _slice.call(arguments);
+  var arrs = [];
+
+  for (var _key = 0; _key < arguments.length; _key++) {
+    arrs[_key] = arguments[_key];
+  }
 };
diff --git a/test/fixtures/transformation/es6-rest-parameters/multiple/expected.js b/test/fixtures/transformation/es6-rest-parameters/multiple/expected.js
index f2f9ea4fe4..56ff1c407f 100644
--- a/test/fixtures/transformation/es6-rest-parameters/multiple/expected.js
+++ b/test/fixtures/transformation/es6-rest-parameters/multiple/expected.js
@@ -1,10 +1,17 @@
 "use strict";
 
-var _slice = Array.prototype.slice;
 var t = function (f) {
-  var items = _slice.call(arguments, 1);
+  var items = [];
+
+  for (var _key = 1; _key < arguments.length; _key++) {
+    items[_key - 1] = arguments[_key];
+  }
 };
 
 function t(f) {
-  var items = _slice.call(arguments, 1);
+  var items = [];
+
+  for (var _key2 = 1; _key2 < arguments.length; _key2++) {
+    items[_key2 - 1] = arguments[_key2];
+  }
 }
diff --git a/test/fixtures/transformation/es6-rest-parameters/single/expected.js b/test/fixtures/transformation/es6-rest-parameters/single/expected.js
index 306e5f6f68..316b3ec9a4 100644
--- a/test/fixtures/transformation/es6-rest-parameters/single/expected.js
+++ b/test/fixtures/transformation/es6-rest-parameters/single/expected.js
@@ -1,10 +1,17 @@
 "use strict";
 
-var _slice = Array.prototype.slice;
 var t = function () {
-  var items = _slice.call(arguments);
+  var items = [];
+
+  for (var _key = 0; _key < arguments.length; _key++) {
+    items[_key] = arguments[_key];
+  }
 };
 
 function t() {
-  var items = _slice.call(arguments);
+  var items = [];
+
+  for (var _key2 = 0; _key2 < arguments.length; _key2++) {
+    items[_key2] = arguments[_key2];
+  }
 }
diff --git a/test/fixtures/transformation/es6-spread/arguments-concat/expected.js b/test/fixtures/transformation/es6-spread/arguments-concat/expected.js
index 1ba8c3aeb2..a95f66cf85 100644
--- a/test/fixtures/transformation/es6-spread/arguments-concat/expected.js
+++ b/test/fixtures/transformation/es6-spread/arguments-concat/expected.js
@@ -2,7 +2,7 @@
 
 var _slice = Array.prototype.slice;
 function foo() {
-  return bar.apply(null, ["test"].concat(_slice.call(arguments)));
+  return bar.apply(undefined, ["test"].concat(_slice.call(arguments)));
 }
 
 function bar(one, two, three) {
diff --git a/test/fixtures/transformation/es6-spread/arguments/expected.js b/test/fixtures/transformation/es6-spread/arguments/expected.js
index c78c808ef0..52a18f07e7 100644
--- a/test/fixtures/transformation/es6-spread/arguments/expected.js
+++ b/test/fixtures/transformation/es6-spread/arguments/expected.js
@@ -1,7 +1,7 @@
 "use strict";
 
 function foo() {
-  return bar.apply(null, arguments);
+  return bar.apply(undefined, arguments);
 }
 
 function bar(one, two, three) {
diff --git a/test/fixtures/transformation/es6-spread/method-call-array-literal/expected.js b/test/fixtures/transformation/es6-spread/method-call-array-literal/expected.js
index 0fd8eaaaf2..a370047756 100644
--- a/test/fixtures/transformation/es6-spread/method-call-array-literal/expected.js
+++ b/test/fixtures/transformation/es6-spread/method-call-array-literal/expected.js
@@ -1,3 +1,3 @@
 "use strict";
 
-f.apply(null, [1, 2, 3]);
+f.apply(undefined, [1, 2, 3]);
diff --git a/test/fixtures/transformation/es6-spread/method-call-first/expected.js b/test/fixtures/transformation/es6-spread/method-call-first/expected.js
index ce4428f54d..1e9fad9adc 100644
--- a/test/fixtures/transformation/es6-spread/method-call-first/expected.js
+++ b/test/fixtures/transformation/es6-spread/method-call-first/expected.js
@@ -4,4 +4,4 @@ var _toArray = function (arr) {
   return Array.isArray(arr) ? arr : Array.from(arr);
 };
 
-add.apply(null, _toArray(numbers).concat([foo, bar]));
+add.apply(undefined, _toArray(numbers).concat([foo, bar]));
diff --git a/test/fixtures/transformation/es6-spread/method-call-middle/expected.js b/test/fixtures/transformation/es6-spread/method-call-middle/expected.js
index 65b6db88be..aadd19e09e 100644
--- a/test/fixtures/transformation/es6-spread/method-call-middle/expected.js
+++ b/test/fixtures/transformation/es6-spread/method-call-middle/expected.js
@@ -4,4 +4,4 @@ var _toArray = function (arr) {
   return Array.isArray(arr) ? arr : Array.from(arr);
 };
 
-add.apply(null, [foo].concat(_toArray(numbers), [bar]));
+add.apply(undefined, [foo].concat(_toArray(numbers), [bar]));
diff --git a/test/fixtures/transformation/es6-spread/method-call-multiple-args/expected.js b/test/fixtures/transformation/es6-spread/method-call-multiple-args/expected.js
index 5f85a3d901..27fe7bf456 100644
--- a/test/fixtures/transformation/es6-spread/method-call-multiple-args/expected.js
+++ b/test/fixtures/transformation/es6-spread/method-call-multiple-args/expected.js
@@ -4,4 +4,4 @@ var _toArray = function (arr) {
   return Array.isArray(arr) ? arr : Array.from(arr);
 };
 
-add.apply(null, [foo, bar].concat(_toArray(numbers)));
+add.apply(undefined, [foo, bar].concat(_toArray(numbers)));
diff --git a/test/fixtures/transformation/es6-spread/method-call-multiple/expected.js b/test/fixtures/transformation/es6-spread/method-call-multiple/expected.js
index 3bf4677ba9..334aa997d7 100644
--- a/test/fixtures/transformation/es6-spread/method-call-multiple/expected.js
+++ b/test/fixtures/transformation/es6-spread/method-call-multiple/expected.js
@@ -4,4 +4,4 @@ var _toArray = function (arr) {
   return Array.isArray(arr) ? arr : Array.from(arr);
 };
 
-add.apply(null, [foo].concat(_toArray(numbers), [bar, what], _toArray(test)));
+add.apply(undefined, [foo].concat(_toArray(numbers), [bar, what], _toArray(test)));
diff --git a/test/fixtures/transformation/es6-spread/method-call-single-arg/expected.js b/test/fixtures/transformation/es6-spread/method-call-single-arg/expected.js
index 4a1da586f0..349be59486 100644
--- a/test/fixtures/transformation/es6-spread/method-call-single-arg/expected.js
+++ b/test/fixtures/transformation/es6-spread/method-call-single-arg/expected.js
@@ -4,4 +4,4 @@ var _toArray = function (arr) {
   return Array.isArray(arr) ? arr : Array.from(arr);
 };
 
-add.apply(null, _toArray(numbers));
+add.apply(undefined, _toArray(numbers));
diff --git a/test/fixtures/transformation/es7-async-functions/LICENSE b/test/fixtures/transformation/es7-async-functions/LICENSE
deleted file mode 100644
index eba1d817f5..0000000000
--- a/test/fixtures/transformation/es7-async-functions/LICENSE
+++ /dev/null
@@ -1,7 +0,0 @@
-Copyright (c) 2014, Facebook, Inc.
-All rights reserved.
-
-This source code is licensed under the BSD-style license found in the
-https://raw.github.com/facebook/regenerator/master/LICENSE file. An
-additional grant of patent rights can be found in the PATENTS file in
-the same directory.
diff --git a/test/fixtures/transformation/es7-async-functions/dependent-promises-should-be-awaitable-out-of-order/exec.js b/test/fixtures/transformation/es7-async-functions/dependent-promises-should-be-awaitable-out-of-order/exec.js
deleted file mode 100644
index ef8e93ddcd..0000000000
--- a/test/fixtures/transformation/es7-async-functions/dependent-promises-should-be-awaitable-out-of-order/exec.js
+++ /dev/null
@@ -1,26 +0,0 @@
-async function outer(value) {
-  var resolved = false;
-  var p1 = new Promise(function(resolve) {
-    setTimeout(function() {
-      resolve(value + 1);
-      resolved = true;
-    }, 0);
-  });
-
-  assert.strictEqual(resolved, false);
-
-  var v2 = await p1.then(function(value) {
-    return value + 1;
-  });
-
-  assert.strictEqual(resolved, true);
-
-  var v1 = await p1;
-
-  return [v1, v2];
-}
-
-outer(1).then(function(pair) {
-  assert.deepEqual(pair, [2, 3]);
-  done();
-}).catch(done);
diff --git a/test/fixtures/transformation/es7-async-functions/nested-async-function-calls-should-evaluate-in-the-right-order/exec.js b/test/fixtures/transformation/es7-async-functions/nested-async-function-calls-should-evaluate-in-the-right-order/exec.js
deleted file mode 100644
index 2e9ac0094f..0000000000
--- a/test/fixtures/transformation/es7-async-functions/nested-async-function-calls-should-evaluate-in-the-right-order/exec.js
+++ /dev/null
@@ -1,40 +0,0 @@
-var markers = [];
-
-async function innerMost(marker) {
-  markers.push(marker);
-  return await marker;
-}
-
-async function inner(marker) {
-  markers.push(marker);
-
-  assert.strictEqual(
-    await innerMost(marker + 1),
-    marker + 1
-  );
-
-  markers.push(marker + 2);
-
-  assert.strictEqual(
-    await innerMost(marker + 3),
-    marker + 3
-  );
-
-  markers.push(marker + 4);
-}
-
-async function outer() {
-  markers.push(0);
-  await inner(1);
-  markers.push(6);
-  await inner(7);
-  markers.push(12);
-}
-
-outer().then(function() {
-  var expected = [];
-  for (var i = 0; i <= 12; ++i)
-    expected.push(i);
-  assert.deepEqual(markers, expected);
-  done();
-}).catch(done);
diff --git a/test/fixtures/transformation/es7-async-functions/no-await-async-function-should-return-a-Promise/exec.js b/test/fixtures/transformation/es7-async-functions/no-await-async-function-should-return-a-Promise/exec.js
deleted file mode 100644
index e4c0a55454..0000000000
--- a/test/fixtures/transformation/es7-async-functions/no-await-async-function-should-return-a-Promise/exec.js
+++ /dev/null
@@ -1,15 +0,0 @@
-var called = false;
-
-async function noAwait(value) {
-  called = true;
-  return value;
-}
-
-var promise = noAwait("asdf");
-assert.strictEqual(called, true);
-
-promise.then(function(value) {
-  assert.strictEqual(called, true);
-  assert.strictEqual(value, "asdf");
-  done();
-}).catch(done);
diff --git a/test/fixtures/transformation/es7-async-functions/one-await-async-function-should-finish-asynchronously/exec.js b/test/fixtures/transformation/es7-async-functions/one-await-async-function-should-finish-asynchronously/exec.js
deleted file mode 100644
index fae186c318..0000000000
--- a/test/fixtures/transformation/es7-async-functions/one-await-async-function-should-finish-asynchronously/exec.js
+++ /dev/null
@@ -1,19 +0,0 @@
-var flag1 = false;
-var flag2 = false;
-
-async function oneAwait(value) {
-  flag1 = true;
-  var result = await value;
-  flag2 = true;
-  return result;
-}
-
-var promise = oneAwait("asdf");
-assert.strictEqual(flag1, true);
-assert.strictEqual(flag2, false);
-
-promise.then(function(value) {
-  assert.strictEqual(flag2, true);
-  assert.strictEqual(value, "asdf");
-  done();
-}).catch(done);
diff --git a/test/fixtures/transformation/es7-async-functions/options.json b/test/fixtures/transformation/es7-async-functions/options.json
deleted file mode 100644
index 8a6dc3a088..0000000000
--- a/test/fixtures/transformation/es7-async-functions/options.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "asyncExec": true,
-  "experimental": true
-}
diff --git a/test/fixtures/transformation/es7-async-functions/rejected-promises-should-be-returned-by-exceptional-async-functions/exec.js b/test/fixtures/transformation/es7-async-functions/rejected-promises-should-be-returned-by-exceptional-async-functions/exec.js
deleted file mode 100644
index 8eb9f6ce33..0000000000
--- a/test/fixtures/transformation/es7-async-functions/rejected-promises-should-be-returned-by-exceptional-async-functions/exec.js
+++ /dev/null
@@ -1,42 +0,0 @@
-var error = new Error("rejected");
-
-async function e(arg) {
-  if (arg) {
-    throw arg;
-  }
-  return "did not throw";
-}
-
-async function f(arg) {
-  return await e(arg);
-}
-
-async function g(arg) {
-  return await f(arg);
-}
-
-async function h(arg) {
-  return await Promise.all([
-    g(arg),
-    Promise.resolve("dummy")
-  ]);
-}
-
-Promise.all([
-  h(error).then(function() {
-    done(new Error("should not have resolved"));
-  }, function(e) {
-    assert.strictEqual(e, error);
-    return "ok1";
-  }),
-  h(null).then(function(result) {
-    assert.deepEqual(result, [
-      "did not throw",
-      "dummy"
-    ]);
-    return "ok2";
-  })
-]).then(function(results) {
-  assert.deepEqual(results, ["ok1", "ok2"]);
-  done();
-}).catch(done);
diff --git a/test/fixtures/transformation/es7-async-functions/rejected-promises-should-cause-await-expressions-to-throw/exec.js b/test/fixtures/transformation/es7-async-functions/rejected-promises-should-cause-await-expressions-to-throw/exec.js
deleted file mode 100644
index 3abf9e0f9d..0000000000
--- a/test/fixtures/transformation/es7-async-functions/rejected-promises-should-cause-await-expressions-to-throw/exec.js
+++ /dev/null
@@ -1,21 +0,0 @@
-var error = new Error("rejected");
-
-async function f(arg) {
-  try {
-    return await arg;
-  } catch (e) {
-    assert.strictEqual(e, error);
-    return "did throw";
-  }
-}
-
-Promise.all([
-  f(Promise.reject(error)),
-  f(Promise.resolve("did not throw"))
-]).then(function(results) {
-  assert.deepEqual(results, [
-    "did throw",
-    "did not throw"
-  ]);
-  done();
-}).catch(done);
diff --git a/test/fixtures/transformation/misc/custom-runtime/actual.js b/test/fixtures/transformation/misc/custom-runtime/actual.js
index a32bce3200..e1ca907ba1 100644
--- a/test/fixtures/transformation/misc/custom-runtime/actual.js
+++ b/test/fixtures/transformation/misc/custom-runtime/actual.js
@@ -1,3 +1,3 @@
-function foo(...test) {
-
+function foo() {
+  test("bar", ...arguments);
 }
diff --git a/test/fixtures/transformation/misc/custom-runtime/expected.js b/test/fixtures/transformation/misc/custom-runtime/expected.js
index 94200c84ce..8139b181c5 100644
--- a/test/fixtures/transformation/misc/custom-runtime/expected.js
+++ b/test/fixtures/transformation/misc/custom-runtime/expected.js
@@ -1,5 +1,5 @@
 "use strict";
 
 function foo() {
-  var test = customNamespace.slice.call(arguments);
+  test.apply(undefined, ["bar"].concat(customNamespace.slice.call(arguments)));
 }
diff --git a/test/fixtures/transformation/misc/runtime/actual.js b/test/fixtures/transformation/misc/runtime/actual.js
index a32bce3200..e1ca907ba1 100644
--- a/test/fixtures/transformation/misc/runtime/actual.js
+++ b/test/fixtures/transformation/misc/runtime/actual.js
@@ -1,3 +1,3 @@
-function foo(...test) {
-
+function foo() {
+  test("bar", ...arguments);
 }
diff --git a/test/fixtures/transformation/misc/runtime/expected.js b/test/fixtures/transformation/misc/runtime/expected.js
index 1427ac1536..cda4ff0fa5 100644
--- a/test/fixtures/transformation/misc/runtime/expected.js
+++ b/test/fixtures/transformation/misc/runtime/expected.js
@@ -1,5 +1,5 @@
 "use strict";
 
 function foo() {
-  var test = to5Runtime.slice.call(arguments);
+  test.apply(undefined, ["bar"].concat(to5Runtime.slice.call(arguments)));
 }
diff --git a/test/fixtures/transformation/optional-async-to-generator/options.json b/test/fixtures/transformation/optional-async-to-generator/options.json
index d8694ba41c..9dbdefeeb0 100644
--- a/test/fixtures/transformation/optional-async-to-generator/options.json
+++ b/test/fixtures/transformation/optional-async-to-generator/options.json
@@ -1,3 +1,4 @@
 {
+  "noCheckAst": true,
   "optional": ["asyncToGenerator"]
 }
diff --git a/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js b/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js
index a672903731..13943a98de 100644
--- a/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js
+++ b/test/fixtures/transformation/optional-bluebird-coroutines/expression/expected.js
@@ -4,8 +4,8 @@ var _interopRequire = function (obj) {
   return obj && (obj["default"] || obj);
 };
 
-var Bluebird = _interopRequire(require("bluebird"));
+var _bluebird = _interopRequire(require("bluebird"));
 
-var foo = Bluebird.coroutine(function* () {
+var foo = _bluebird.coroutine(function* () {
   var wat = yield bar();
 });
diff --git a/test/fixtures/transformation/optional-bluebird-coroutines/options.json b/test/fixtures/transformation/optional-bluebird-coroutines/options.json
index 264ef8fbf1..beb0408342 100644
--- a/test/fixtures/transformation/optional-bluebird-coroutines/options.json
+++ b/test/fixtures/transformation/optional-bluebird-coroutines/options.json
@@ -1,3 +1,4 @@
 {
-  "optional": ["bluebirdCoroutines"]
+  "optional": ["bluebirdCoroutines"],
+  "noCheckAst": true
 }
diff --git a/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js b/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js
index 65d8cff6ef..9b200b29f0 100644
--- a/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js
+++ b/test/fixtures/transformation/optional-bluebird-coroutines/statement/expected.js
@@ -4,8 +4,8 @@ var _interopRequire = function (obj) {
   return obj && (obj["default"] || obj);
 };
 
-var Bluebird = _interopRequire(require("bluebird"));
+var _bluebird = _interopRequire(require("bluebird"));
 
-var foo = Bluebird.coroutine(function* foo() {
+var foo = _bluebird.coroutine(function* foo() {
   var wat = yield bar();
 });
diff --git a/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js b/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js
index 6a66b4e972..9de37223a2 100644
--- a/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js
+++ b/test/fixtures/transformation/optional-proto-to-assign/assignment-expression/expected.js
@@ -1,6 +1,6 @@
 "use strict";
 
-var _foo, _foo$bar, _foo2;
+var _foo, _foo$bar, _foo$bar2;
 var _defaults = function (obj, defaults) {
   for (var key in defaults) {
     if (obj[key] === undefined) {
@@ -15,4 +15,4 @@ console.log((_foo = foo, _defaults(_foo, bar), _foo));
 
 console.log((_foo$bar = foo[bar], _defaults(_foo$bar, bar), _foo$bar));
 
-console.log((_foo2 = foo[bar()], _defaults(_foo2, bar), _foo2));
+console.log((_foo$bar2 = foo[bar()], _defaults(_foo$bar2, bar), _foo$bar2));
diff --git a/test/fixtures/transformation/optional-proto-to-assign/class/expected.js b/test/fixtures/transformation/optional-proto-to-assign/class/expected.js
index 2f4501d427..2d7d562265 100644
--- a/test/fixtures/transformation/optional-proto-to-assign/class/expected.js
+++ b/test/fixtures/transformation/optional-proto-to-assign/class/expected.js
@@ -11,6 +11,9 @@ var _defaults = function (obj, defaults) {
 };
 
 var _inherits = function (child, parent) {
+  if (typeof parent !== "function" && parent !== null) {
+    throw new TypeError("Super expression must either be null or a function, not " + typeof parent);
+  }
   child.prototype = Object.create(parent && parent.prototype, {
     constructor: {
       value: child,
@@ -25,7 +28,7 @@ var _inherits = function (child, parent) {
 var Foo = (function () {
   var _Bar = Bar;
   var Foo = function Foo() {
-    if (_Bar) {
+    if (_Bar !== null) {
       _Bar.apply(this, arguments);
     }
   };
diff --git a/test/fixtures/transformation/optional-typeof-symbol/basic/actual.js b/test/fixtures/transformation/optional-typeof-symbol/basic/actual.js
new file mode 100644
index 0000000000..20422ebc64
--- /dev/null
+++ b/test/fixtures/transformation/optional-typeof-symbol/basic/actual.js
@@ -0,0 +1,2 @@
+var s = Symbol("s");
+assert.equal(typeof s, "symbol");
diff --git a/test/fixtures/transformation/optional-typeof-symbol/basic/exec.js b/test/fixtures/transformation/optional-typeof-symbol/basic/exec.js
new file mode 100644
index 0000000000..20422ebc64
--- /dev/null
+++ b/test/fixtures/transformation/optional-typeof-symbol/basic/exec.js
@@ -0,0 +1,2 @@
+var s = Symbol("s");
+assert.equal(typeof s, "symbol");
diff --git a/test/fixtures/transformation/optional-typeof-symbol/basic/expected.js b/test/fixtures/transformation/optional-typeof-symbol/basic/expected.js
new file mode 100644
index 0000000000..c33ed64571
--- /dev/null
+++ b/test/fixtures/transformation/optional-typeof-symbol/basic/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var _typeof = function (obj) {
+  return obj && obj.constructor === Symbol ? "symbol" : typeof obj;
+};
+
+var s = Symbol("s");
+assert.equal(_typeof(s), "symbol");
diff --git a/test/fixtures/transformation/optional-typeof-symbol/options.json b/test/fixtures/transformation/optional-typeof-symbol/options.json
new file mode 100644
index 0000000000..6e208aa132
--- /dev/null
+++ b/test/fixtures/transformation/optional-typeof-symbol/options.json
@@ -0,0 +1,3 @@
+{
+  "optional": ["typeofSymbol"]
+}
diff --git a/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js b/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
index 4d9647c912..fbb64ac4f8 100644
--- a/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
+++ b/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
@@ -1,6 +1,6 @@
 "use strict";
 
-var _obj2, _obj4, _ref2, _obj6, _ref4;
+var _obj2, _obj4, _x2, _obj$y2, _x4;
 var _hasOwn = Object.prototype.hasOwnProperty;
 var obj = {};
 
@@ -11,17 +11,17 @@ if (!_hasOwn.call(_obj, "x")) _obj.x = 2;
 console.log((_obj2 = obj, !_hasOwn.call(_obj2, "x") && (_obj2.x = 2), _obj2.x));
 
 var _obj3 = obj;
-var _ref = x();
+var _x = x();
 
-if (!_hasOwn.call(_obj3, _ref)) _obj3[_ref] = 2;
+if (!_hasOwn.call(_obj3, _x)) _obj3[_x] = 2;
 
 
-console.log((_obj4 = obj, _ref2 = x(), !_hasOwn.call(_obj4, _ref2) && (_obj4[_ref2] = 2), _obj4[_ref2]));
+console.log((_obj4 = obj, _x2 = x(), !_hasOwn.call(_obj4, _x2) && (_obj4[_x2] = 2), _obj4[_x2]));
 
-var _obj5 = obj[y()];
-var _ref3 = x();
+var _obj$y = obj[y()];
+var _x3 = x();
 
-if (!_hasOwn.call(_obj5, _ref3)) _obj5[_ref3] = 2;
+if (!_hasOwn.call(_obj$y, _x3)) _obj$y[_x3] = 2;
 
 
-console.log((_obj6 = obj[y()], _ref4 = x(), !_hasOwn.call(_obj6, _ref4) && (_obj6[_ref4] = 2), _obj6[_ref4]));
+console.log((_obj$y2 = obj[y()], _x4 = x(), !_hasOwn.call(_obj$y2, _x4) && (_obj$y2[_x4] = 2), _obj$y2[_x4]));
diff --git a/test/fixtures/transformation/playground/method-binding/expected.js b/test/fixtures/transformation/playground/method-binding/expected.js
index f103f4683f..156bcfffd5 100644
--- a/test/fixtures/transformation/playground/method-binding/expected.js
+++ b/test/fixtures/transformation/playground/method-binding/expected.js
@@ -1,11 +1,11 @@
 "use strict";
 
-var _obj, _obj2, _obj$foo, _obj$foo2, _obj3, _args, _args2, _args3;
+var _obj, _obj2, _obj$foo, _obj$foo2, _obj$foo3, _args, _args2, _args3;
 var fn = (_obj = obj, _obj.method.bind(_obj));
 var fn = (_obj2 = obj, _obj2.method.bind(_obj2, "foob"));
 var fn = (_obj$foo = obj[foo], _obj$foo.method.bind(_obj$foo));
 var fn = (_obj$foo2 = obj.foo, _obj$foo2.method.bind(_obj$foo2));
-var fn = (_obj3 = obj[foo()], _obj3.method.bind(_obj3));
+var fn = (_obj$foo3 = obj[foo()], _obj$foo3.method.bind(_obj$foo3));
 
 ["foo", "bar"].map((_args = [], function (_val) {
   return _val.toUpperCase();
diff --git a/test/fixtures/transformation/spec-no-duplicate-properties/identifiers/actual.js b/test/fixtures/transformation/spec-no-duplicate-properties/identifiers/actual.js
deleted file mode 100644
index 7dd5168e50..0000000000
--- a/test/fixtures/transformation/spec-no-duplicate-properties/identifiers/actual.js
+++ /dev/null
@@ -1 +0,0 @@
-var obj = { a: 1, a: 2 };
diff --git a/test/fixtures/transformation/spec-no-duplicate-properties/literals/actual.js b/test/fixtures/transformation/spec-no-duplicate-properties/literals/actual.js
deleted file mode 100644
index 85b7f9f02a..0000000000
--- a/test/fixtures/transformation/spec-no-duplicate-properties/literals/actual.js
+++ /dev/null
@@ -1 +0,0 @@
-var obj = { "a": 1, "a": 2 };
diff --git a/test/fixtures/transformation/spec-no-duplicate-properties/mixed/actual.js b/test/fixtures/transformation/spec-no-duplicate-properties/mixed/actual.js
deleted file mode 100644
index eace9c1b04..0000000000
--- a/test/fixtures/transformation/spec-no-duplicate-properties/mixed/actual.js
+++ /dev/null
@@ -1 +0,0 @@
-var obj = { a: 1, "a": 2 };
diff --git a/test/fixtures/transformation/spec-no-duplicate-properties/options.json b/test/fixtures/transformation/spec-no-duplicate-properties/options.json
deleted file mode 100644
index 32dce7785e..0000000000
--- a/test/fixtures/transformation/spec-no-duplicate-properties/options.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "throws": "Duplicate property key"
-}
diff --git a/test/fixtures/transformation/spec-no-for-in-of-assignment/in/actual.js b/test/fixtures/transformation/spec-no-for-in-of-assignment/in/actual.js
deleted file mode 100644
index 167407a7da..0000000000
--- a/test/fixtures/transformation/spec-no-for-in-of-assignment/in/actual.js
+++ /dev/null
@@ -1,3 +0,0 @@
-for (var i = 0 in obj) {
-
-}
diff --git a/test/fixtures/transformation/spec-no-for-in-of-assignment/of/actual.js b/test/fixtures/transformation/spec-no-for-in-of-assignment/of/actual.js
deleted file mode 100644
index 56e4dfef82..0000000000
--- a/test/fixtures/transformation/spec-no-for-in-of-assignment/of/actual.js
+++ /dev/null
@@ -1,3 +0,0 @@
-for (var i = 0 of obj) {
-
-}
diff --git a/test/fixtures/transformation/spec-no-for-in-of-assignment/options.json b/test/fixtures/transformation/spec-no-for-in-of-assignment/options.json
deleted file mode 100644
index c7ae9b8aa4..0000000000
--- a/test/fixtures/transformation/spec-no-for-in-of-assignment/options.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "throws": "No assignments allowed in for-in/of head"
-}
diff --git a/test/fixtures/transformation/spec/block-hoist-functions/exec.js b/test/fixtures/transformation/spec/block-hoist-functions/exec.js
deleted file mode 100644
index f3475e0a9e..0000000000
--- a/test/fixtures/transformation/spec/block-hoist-functions/exec.js
+++ /dev/null
@@ -1,5 +0,0 @@
-function f() { return 1; }
-{
-  function f() { return 2; }
-}
-assert.equal(f(), 1);
diff --git a/test/mocha.opts b/test/mocha.opts
index 51c30180df..850a6c2f64 100644
--- a/test/mocha.opts
+++ b/test/mocha.opts
@@ -1,4 +1,2 @@
 --reporter dot
 --ui tdd
---check-leaks
---globals regeneratorRuntime
diff --git a/test/regenerator.js b/test/regenerator.js
new file mode 100644
index 0000000000..2a2481cba7
--- /dev/null
+++ b/test/regenerator.js
@@ -0,0 +1,23 @@
+if (!process.env.ALL_6TO5_TESTS) return;
+
+require("../register")({
+  blacklist: ["useStrict"],
+  experimental: true
+});
+
+var transform = require("../lib/6to5/transformation/transform");
+var fs        = require("fs");
+var _         = require("lodash");
+
+var regeneratorLoc = __dirname + "/../vendor/regenerator";
+
+if (!fs.existsSync(regeneratorLoc)) {
+  console.error("No vendor/regenerator - run `git submodule update --init && cd vendor/regenerator && npm install`");
+  process.exit(1);
+}
+
+_.each(["tests", "async"], function (filename) {
+  var loc = regeneratorLoc + "/test/" + filename + ".es6.js";
+  var code = fs.readFileSync(loc, "utf8");
+  require(loc);
+});
diff --git a/test/traceur.js b/test/traceur.js
new file mode 100644
index 0000000000..a52e2deaad
--- /dev/null
+++ b/test/traceur.js
@@ -0,0 +1,59 @@
+if (!process.env.ALL_6TO5_TESTS) return;
+
+var fs = require("fs");
+var _  = require("lodash");
+
+var traceurLoc = __dirname + "/../vendor/traceur";
+if (!fs.existsSync(traceurLoc)) {
+  console.error("No vendor/traceur - run `git submodule update --init`");
+  process.exit(1);
+}
+
+require("./_transformation-helper")({
+  name: "traceur",
+  loc: traceurLoc + "/test/feature",
+
+  ignoreSuites: [
+    "ObjectMixin",
+    "Annotations",
+    "TestRunner",
+    "Tools",
+    "TempVarTransformer",
+    "AtScript",
+    "FreeVariableChecker",
+    "TypeAssertions",
+    "MemberVariables",
+    "Types"
+  ],
+
+  ignoreTasks: [
+    // core.js doesn't support due to a perf hit and having to override a lot
+    // of native methods
+    "Symbol/GetOwnPropertySymbols",
+
+    // traceur doesn't name methods and has an incorrect test asserting that
+    // they have no names
+    "PropertyMethodAssignment/PropertyMethodAssignment",
+
+    // 6to5 assumes that all code transformed is a module
+    "Strict",
+    "Syntax/UseStrictEscapeSequence",
+    "Syntax/UseStrictLineContinuation",
+
+    // the spec for these doesn't define syntax (as far as i could tell)
+    // these both fail because of filter between blocks
+    "ArrayComprehension/Simple",
+    "GeneratorComprehension/Simple"
+  ]
+}, {
+  optional: ["typeofSymbol"],
+  experimental: true,
+  after: function () {
+    // StringExtras/StarsWith
+    delete Object.prototype[1];
+  }
+}, function (opts, task) {
+  if (!_.contains(task.exec.loc, "module.js")) {
+    opts.blacklist = ["useStrict"];
+  }
+});
diff --git a/test/transformation.js b/test/transformation.js
index 8bed3f56c1..642604401e 100644
--- a/test/transformation.js
+++ b/test/transformation.js
@@ -1,100 +1,3 @@
-var genHelpers = require("./_generator-helpers");
-var transform  = require("../lib/6to5/transformation/transform");
-var sourceMap  = require("source-map");
-var helper     = require("./_helper");
-var assert     = require("assert");
-var chai       = require("chai");
-var util       = require("../lib/6to5/util");
-var _          = require("lodash");
-
-require("../lib/6to5/polyfill");
-
-var run = function (task, done) {
-  var actual = task.actual;
-  var expect = task.expect;
-  var exec   = task.exec;
-  var opts   = task.options;
-
-  var getOpts = function (self) {
-    return _.merge({
-      filename: self.loc
-    }, opts);
-  };
-
-  var execCode = exec.code;
-  var result;
-
-  if (execCode) {
-    result = transform(execCode, getOpts(exec));
-    execCode = result.code;
-
-    try {
-      var fn = new Function("assert", "done", "genHelpers", execCode);
-      fn(assert, done, genHelpers);
-    } catch (err) {
-      err.message = exec.loc + ": " + err.message;
-      err.message += util.codeFrame(execCode);
-      throw err;
-    }
-  }
-
-  var actualCode = actual.code;
-  var expectCode = expect.code;
-  if (!execCode || actualCode) {
-    result     = transform(actualCode, getOpts(actual));
-    actualCode = result.code;
-
-    chai.expect(actualCode).to.be.equal(expectCode, actual.loc + " !== " + expect.loc);
-  }
-
-  if (task.sourceMap) {
-    chai.expect(result.map).to.deep.equal(task.sourceMap);
-  }
-
-  if (task.sourceMappings) {
-    var consumer = new sourceMap.SourceMapConsumer(result.map);
-
-    _.each(task.sourceMappings, function (mapping, i) {
-      var expect = mapping.original;
-
-      var actual = consumer.originalPositionFor(mapping.generated);
-      chai.expect({ line: actual.line, column: actual.column }).to.deep.equal(expect);
-    });
-  }
-};
-
-_.each(helper.get("transformation"), function (testSuite) {
-  suite("transformation/" + testSuite.title, function () {
-    _.each(testSuite.tests, function (task) {
-      var runTest = function (done) {
-        var runTask = function () {
-          run(task, done);
-        };
-
-        var throwMsg = task.options.throws;
-        if (throwMsg) {
-          // internal api doesn't have this option but it's best not to pollute
-          // the options object with useless options
-          delete task.options.throws;
-
-          assert.throws(runTask, function (err) {
-            return err.message.indexOf(throwMsg) >= 0;
-          });
-        } else {
-          runTask();
-        }
-      };
-
-      var callback;
-      if (task.options.asyncExec) {
-        callback = runTest;
-      } else {
-        callback = function () {
-          return runTest();
-        };
-      }
-
-      test(task.title, !task.disabled && callback);
-    });
-  });
+require("./_transformation-helper")({
+  name: "transformation"
 });
diff --git a/test/util.js b/test/util.js
index 4d4913547d..4f2fead371 100644
--- a/test/util.js
+++ b/test/util.js
@@ -18,6 +18,10 @@ suite("util", function () {
     assert.ok(util.canCompile("/test.es6"));
     assert.ok(util.canCompile("/scripts/test.es6"));
 
+    assert.ok(util.canCompile("test.es"));
+    assert.ok(util.canCompile("/test.es"));
+    assert.ok(util.canCompile("/scripts/test.es"));
+
     assert.ok(!util.canCompile("test"));
     assert.ok(!util.canCompile("test.css"));
     assert.ok(!util.canCompile("/test.css"));
diff --git a/vendor/regenerator b/vendor/regenerator
new file mode 160000
index 0000000000..45829598be
--- /dev/null
+++ b/vendor/regenerator
@@ -0,0 +1 @@
+Subproject commit 45829598be68fa4cb10f86b5ca13aa7284aa6bc8
diff --git a/vendor/traceur b/vendor/traceur
new file mode 160000
index 0000000000..0c3dad3ae2
--- /dev/null
+++ b/vendor/traceur
@@ -0,0 +1 @@
+Subproject commit 0c3dad3ae217139b1a6b4b986cef57669e7b49c6