Rename test fixtures using module syntax to .mjs files.

packages/babel-plugin-transform-function-name/test/fixtures/function-name/modules-3/input.mjs

@@ -0,0 +1,7 @@
+import {getForm} from "./store"
+
+export default class Login extends React.Component {
+  getForm() {
+    return getForm().toJS()
+  }
+}