Check that a document with type "text/x-pseudo-xml" is not parsed as XML.
Do XML documents fetched using XMLHttpRequest have script run? Have XML Stylesheet PIs loaded?
Do responseXML and responseText return null or raise exceptions when not ready?
Does .abort() send readyState to 0 and leave the event listeners?
Do headers with U+000A, U+000D, U+0020, U+003A characters cause it to be dropped?