This tests the constructor property of DOM objects: http://bugs.webkit.org/show_bug.cgi?id=11315 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS window.document.constructor === window.Object is false PASS window.document.constructor === window.HTMLDocument is true PASS window.document.constructor.prototype === window.HTMLDocument.prototype is true PASS window.document.constructor.prototype.__proto__ === window.HTMLDocument.prototype.__proto__ is true PASS window.document.constructor.prototype.__proto__ === window.Document.prototype is true PASS window.document.body.constructor === window.HTMLBodyElement is true PASS window.document.body.constructor.prototype === window.HTMLBodyElement.prototype is true PASS window.document.body.constructor.prototype.__proto__ === window.HTMLBodyElement.prototype.__proto__ is true PASS window.document.body.constructor.prototype.__proto__ === window.HTMLElement.prototype is true PASS nodeList.constructor === window.NodeList is true PASS nodeList.constructor.prototype === window.NodeList.prototype is true PASS mutationEvent.constructor === window.MutationEvent is true PASS mutationEvent.constructor.prototype.__proto__ === window.Event.prototype is true PASS successfullyParsed is true TEST COMPLETE