diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/for-of/string-iterator-surfaces.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/for-of/string-iterator-surfaces.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,76 @@
+// String.prototype[@@iterator] and StringIterator.prototype surface tests
+
+load(libdir + "array-compare.js");
+load(libdir + "asserts.js");
+load(libdir + "iteration.js");
+
+function assertDataDescriptor(actual, expected) {
+    assertEq(actual.value, expected.value);
+    assertEq(actual.writable, expected.writable);
+    assertEq(actual.enumerable, expected.enumerable);
+    assertEq(actual.configurable, expected.configurable);
+}
+
+function isConstructor(o) {
+    try {
+        new (new Proxy(o, {construct: () => ({})}));
+        return true;
+    } catch(e) {
+        return false;
+    }
+}
+
+function assertBuiltinFunction(o, name, arity) {
+    var fn = o[name];
+    assertDataDescriptor(Object.getOwnPropertyDescriptor(o, name), {
+        value: fn,
+        writable: true,
+        enumerable: false,
+        configurable: true,
+    });
+
+    assertEq(typeof fn, "function");
+    assertEq(Object.getPrototypeOf(fn), Function.prototype);
+    // FIXME: Proxy should only have [[Construct]] if target has [[Construct]] (bug 929467)
+    // assertEq(isConstructor(fn), false);
+
+    arraysEqual(Object.getOwnPropertyNames(fn).sort(), ["length", "name", "arguments", "caller"].sort());
+
+    // Also test "name", "arguments" and "caller" in addition to "length"?
+    assertDataDescriptor(Object.getOwnPropertyDescriptor(fn, "length"), {
+        value: arity,
+        writable: false,
+        enumerable: false,
+        configurable: false,
+    });
+}
+
+
+// String.prototype[@@iterator] is a built-in function
+assertBuiltinFunction(String.prototype, std_iterator, 0);
+
+// Test StringIterator.prototype surface
+var iter = ""[std_iterator]();
+var iterProto = Object.getPrototypeOf(iter);
+
+// StringIterator.prototype inherits from Object.prototype
+assertEq(Object.getPrototypeOf(iterProto), Object.prototype);
+
+// Own properties for StringIterator.prototype: "next" and @@iterator
+arraysEqual(Object.getOwnPropertyNames(iterProto).sort(), ["next", std_iterator].sort());
+
+// StringIterator.prototype[@@iterator] is a built-in function
+assertBuiltinFunction(iterProto, std_iterator, 0);
+
+// StringIterator.prototype.next is a built-in function
+assertBuiltinFunction(iterProto, "next", 0);
+
+// StringIterator.prototype[@@iterator] is generic and returns |this|
+for (var v of [void 0, null, true, false, "", 0, 1, {}, [], iter, iterProto]) {
+    assertEq(iterProto[std_iterator].call(v), v);
+}
+
+// StringIterator.prototype.next is not generic
+for (var v of [void 0, null, true, false, "", 0, 1, {}, [], iterProto]) {
+    assertThrowsInstanceOf(() => iterProto.next.call(v), TypeError);
+}