This tests that the querySelector and querySelectorAll fast path for IDs is not overzelous. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS document.querySelector('div#testid') is correctNode PASS document.querySelector('#testid') is correctNode PASS document.querySelector('ul#testid') is null PASS document.querySelector('ul #testid') is null PASS document.querySelector('#testid[attr]') is null PASS document.querySelector('#testid:not(div)') is null PASS document.querySelectorAll('div#testid').length is 1 PASS document.querySelectorAll('div#testid').item(0) is correctNode PASS document.querySelectorAll('#testid').length is 1 PASS document.querySelectorAll('#testid').item(0) is correctNode PASS document.querySelectorAll('ul#testid').length is 0 PASS document.querySelectorAll('ul #testid').length is 0 PASS document.querySelectorAll('#testid[attr]').length is 0 PASS document.querySelectorAll('#testid:not(div)').length is 0 PASS successfullyParsed is true TEST COMPLETE