diff --git a/packages/babel-core/test/caching-api.js b/packages/babel-core/test/caching-api.js
new file mode 100644
index 0000000000..914214540b
--- /dev/null
+++ b/packages/babel-core/test/caching-api.js
@@ -0,0 +1,356 @@
+import assert from "assert";
+import { makeStrongCache } from "../lib/config/caching";
+
+describe("caching API", () => {
+  it("should allow permacaching with .forever()", () => {
+    let count = 0;
+
+    const fn = makeStrongCache((arg, cache) => {
+      cache.forever();
+      return { arg, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    assert.notEqual(fn("one"), fn("two"));
+  });
+
+  it("should allow permacaching with cache(true)", () => {
+    let count = 0;
+
+    const fn = makeStrongCache((arg, cache) => {
+      cache(true);
+      return { arg, count: count++ };
+    });
+
+
+    assert.deepEqual(fn("one"), { arg: "one", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    assert.notEqual(fn("one"), fn("two"));
+  });
+
+  it("should allow disabling caching with .never()", () => {
+    let count = 0;
+
+    const fn = makeStrongCache((arg, cache) => {
+      cache.never();
+      return { arg, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", count: 0 });
+    assert.deepEqual(fn("one"), { arg: "one", count: 1 });
+    assert.notEqual(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", count: 4 });
+    assert.deepEqual(fn("two"), { arg: "two", count: 5 });
+    assert.notEqual(fn("two"), fn("two"));
+
+    assert.notEqual(fn("one"), fn("two"));
+  });
+
+  it("should allow disabling caching with cache(false)", () => {
+    let count = 0;
+
+    const fn = makeStrongCache((arg, cache) => {
+      cache(false);
+      return { arg, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", count: 0 });
+    assert.deepEqual(fn("one"), { arg: "one", count: 1 });
+    assert.notEqual(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", count: 4 });
+    assert.deepEqual(fn("two"), { arg: "two", count: 5 });
+    assert.notEqual(fn("two"), fn("two"));
+
+    assert.notEqual(fn("one"), fn("two"));
+  });
+
+  it("should allow caching based on a value with .using(fn)", () => {
+    let count = 0;
+    let other = "default";
+
+    const fn = makeStrongCache((arg, cache) => {
+      const val = cache.using(() => other);
+
+      return { arg, val, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", count: 2 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", count: 3 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "default";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", count: 2 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", count: 3 });
+    assert.equal(fn("two"), fn("two"));
+  });
+
+  it("should allow caching based on a value with cache(fn)", () => {
+    let count = 0;
+    let other = "default";
+
+    const fn = makeStrongCache((arg, cache) => {
+      const val = cache(() => other);
+
+      return { arg, val, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", count: 2 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", count: 3 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "default";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", count: 2 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", count: 3 });
+    assert.equal(fn("two"), fn("two"));
+  });
+
+  it("should allow invalidation based on a value with .invalidate(fn)", () => {
+    let count = 0;
+    let other = "default";
+
+    const fn = makeStrongCache((arg, cache) => {
+      const val = cache.invalidate(() => other);
+
+      return { arg, val, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", count: 2 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", count: 3 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "default";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", count: 4 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", count: 5 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", count: 6 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", count: 7 });
+    assert.equal(fn("two"), fn("two"));
+  });
+
+  it("should allow invalidation with .using and .invalidate", () => {
+    let count = 0;
+    let other = "default";
+    let another = "another";
+
+    const fn = makeStrongCache((arg, cache) => {
+      const val = cache.using(() => other);
+      const val2 = cache.invalidate(() => another);
+
+      return { arg, val, val2, count: count++ };
+    });
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", val2: "another", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", val2: "another", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", val2: "another", count: 2 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", val2: "another", count: 3 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "default";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "default", val2: "another", count: 4 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "default", val2: "another", count: 5 });
+    assert.equal(fn("two"), fn("two"));
+
+    other = "new";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", val2: "another", count: 6 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", val2: "another", count: 7 });
+    assert.equal(fn("two"), fn("two"));
+
+    another = "second";
+
+    assert.deepEqual(fn("one"), { arg: "one", val: "new", val2: "second", count: 8 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", val: "new", val2: "second", count: 9 });
+    assert.equal(fn("two"), fn("two"));
+
+  });
+
+  it("should throw if caching is never configured and not defaulting", () => {
+    const fn = makeStrongCache(() => { }, false /* autoPermacache */);
+
+    assert.throws(() => fn(), /Error: Caching was left unconfigured./);
+  });
+
+  it("should auto-permacache by default", () => {
+    let count = 0;
+
+    const fn = makeStrongCache((arg) => ({ arg, count: count++ }));
+
+    assert.deepEqual(fn("one"), { arg: "one", count: 0 });
+    assert.equal(fn("one"), fn("one"));
+
+    assert.deepEqual(fn("two"), { arg: "two", count: 1 });
+    assert.equal(fn("two"), fn("two"));
+
+    assert.notEqual(fn("one"), fn("two"));
+  });
+
+  it("should throw if you set permacaching and use .using", () => {
+    const fn = makeStrongCache((arg, cache) => {
+      cache.forever();
+
+      cache.using(() => null);
+    });
+
+    assert.throws(() => fn(), /Caching has already been configured/);
+  });
+
+  it("should throw if you set permacaching and use .invalidate", () => {
+    const fn = makeStrongCache((arg, cache) => {
+      cache.forever();
+
+      cache.invalidate(() => null);
+    });
+
+    assert.throws(() => fn(), /Caching has already been configured/);
+  });
+
+  it("should throw if you set permacaching and use .never", () => {
+    const fn = makeStrongCache((arg, cache) => {
+      cache.forever();
+
+      cache.never();
+    });
+
+    assert.throws(() => fn(), /Caching has already been configured/);
+  });
+
+  it("should throw if you set no caching and use .using", () => {
+    const fn = makeStrongCache((arg, cache) => {
+      cache.never();
+
+      cache.using(() => null);
+    });
+
+    assert.throws(() => fn(), /Caching has already been configured/);
+  });
+
+  it("should throw if you set no caching and use .invalidate", () => {
+    const fn = makeStrongCache((arg, cache) => {
+      cache.never();
+
+      cache.invalidate(() => null);
+    });
+
+    assert.throws(() => fn(), /Caching has already been configured/);
+  });
+
+  it("should throw if you set no caching and use .never", () => {
+    const fn = makeStrongCache((arg, cache) => {
+      cache.never();
+
+      cache.using(() => null);
+    });
+
+    assert.throws(() => fn(), /Caching has already been configured/);
+  });
+
+  it("should throw if you configure .forever after exiting", () => {
+    const fn = makeStrongCache((arg, cache) => cache);
+
+    assert.throws(() => fn().forever(), /Cannot change caching after evaluation/);
+  });
+
+  it("should throw if you configure .never after exiting", () => {
+    const fn = makeStrongCache((arg, cache) => cache);
+
+    assert.throws(() => fn().never(), /Cannot change caching after evaluation/);
+  });
+
+  it("should throw if you configure .using after exiting", () => {
+    const fn = makeStrongCache((arg, cache) => cache);
+
+    assert.throws(() => fn().using(() => null), /Cannot change caching after evaluation/);
+  });
+
+  it("should throw if you configure .invalidate after exiting", () => {
+    const fn = makeStrongCache((arg, cache) => cache);
+
+    assert.throws(() => fn().invalidate(() => null), /Cannot change caching after evaluation/);
+  });
+});
diff --git a/packages/babel-core/test/config-chain.js b/packages/babel-core/test/config-chain.js
index 1aeed5f4d0..453e3e86e6 100644
--- a/packages/babel-core/test/config-chain.js
+++ b/packages/babel-core/test/config-chain.js
@@ -418,6 +418,46 @@ describe("buildConfigChain", function () {
     assert.deepEqual(chain, expected);
   });
 
+  it("js-config-function", function () {
+    const chain = buildConfigChain({
+      filename: fixture("js-config-function", "src.js"),
+    });
+
+    const expected = [
+      {
+        type: "options",
+        options: {
+          ignore: [
+            "root-ignore",
+          ],
+        },
+        alias: fixture(".babelignore"),
+        loc: fixture(".babelignore"),
+        dirname: fixture(),
+      },
+      {
+        type: "options",
+        options: {
+          compact: true,
+        },
+        alias: fixture("js-config-function", ".babelrc.js"),
+        loc: fixture("js-config-function", ".babelrc.js"),
+        dirname: fixture("js-config-function"),
+      },
+      {
+        type: "arguments",
+        options: {
+          filename: fixture("js-config-function", "src.js"),
+        },
+        alias: "base",
+        loc: "base",
+        dirname: base(),
+      },
+    ];
+
+    assert.deepEqual(chain, expected);
+  });
+
   it("js-config-default - should read transpiled export default", function () {
     const chain = buildConfigChain({
       filename: fixture("js-config-default", "src.js"),
diff --git a/packages/babel-core/test/fixtures/config/js-config-function/.babelrc.js b/packages/babel-core/test/fixtures/config/js-config-function/.babelrc.js
new file mode 100644
index 0000000000..73ace51a11
--- /dev/null
+++ b/packages/babel-core/test/fixtures/config/js-config-function/.babelrc.js
@@ -0,0 +1,7 @@
+module.exports = function(api) {
+  api.cache(true);
+
+  return {
+    compact: true,
+  };
+};