This tests that setting the proto of a built in constructor is not reset On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". proto = new Number(42): 42 Object.getPrototypeOf(WorkerLocation): function () {} { [native code] } WorkerLocation.__proto__ = proto: 42 Object.getPrototypeOf(WorkerLocation): 42 PASS successfullyParsed is true TEST COMPLETE