Inserting DocumentFragments should remove all children of the fragment before inserting the children. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". Testing appendChild PASS mutations.length is 2 PASS mutations[0].addedNodes.length is 0 PASS mutations[0].removedNodes.length is 2 PASS mutations[1].addedNodes.length is 2 PASS mutations[1].removedNodes.length is 0 Testing insertBefore PASS mutations.length is 2 PASS mutations[0].addedNodes.length is 0 PASS mutations[0].removedNodes.length is 2 PASS mutations[1].addedNodes.length is 2 PASS mutations[1].removedNodes.length is 0 Testing replaceChild PASS mutations.length is 2 PASS mutations[0].addedNodes.length is 0 PASS mutations[0].removedNodes.length is 2 PASS mutations[1].addedNodes.length is 2 PASS mutations[1].removedNodes.length is 1 PASS successfullyParsed is true TEST COMPLETE