Make sure that event targets get cleared after dispatching in a shadow tree. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS undefined is undefined. PASS counter++ is 0 PASS window.event is undefined. PASS counter++ is 1 PASS window.event is undefined. PASS counter++ is 2 PASS counter is 3 PASS event.target is null PASS event.relatedTarget is null PASS successfullyParsed is true TEST COMPLETE