HTMLFormElement::checkValidity() with cases that event handlers called by checkValidity() updates DOM structure. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". The target form is removed. PASS document.getElementById("f1").checkValidity() is false A control to be checked is removed. PASS document.getElementById("f1").checkValidity() is false PASS handler2Called is false A new control is added. PASS document.getElementById("f1").checkValidity() is false PASS handler2Called is false A control is moved to another form. PASS document.getElementById("f1").checkValidity() is false PASS handler2Called is false A control is moved to another document. PASS document.getElementById("f1").checkValidity() is true PASS successfullyParsed is true TEST COMPLETE