This test checks that setting a non-object, non-null value for __proto__ does not lead to a crash when next setting a property on the object. This was reported as bug 17925. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS x.__proto__ is originalProto If we got to this point then we did not crash and the test has passed. PASS successfullyParsed is true TEST COMPLETE