DOMException needs a real prototype: http://bugs.webkit.org/show_bug.cgi?id=16637 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS e.toString() is "Error: HIERARCHY_REQUEST_ERR: DOM Exception 3" PASS Object.prototype.toString.call(e) is "[object DOMException]" PASS Object.prototype.toString.call(e.__proto__) is "[object DOMExceptionPrototype]" PASS e.constructor.toString() is "[object DOMExceptionConstructor]" PASS e.constructor is window.DOMException PASS e.HIERARCHY_REQUEST_ERR is e.constructor.HIERARCHY_REQUEST_ERR PASS e.HIERARCHY_REQUEST_ERR is 3 PASS successfullyParsed is true TEST COMPLETE