...looking at <http://tc.labs.opera.com/apis/XMLHttpRequest/responseXML/006.htm>...
It seems there are no test cases that check that a user agent either correctly handles unknown method names, or rejects them with an SECURITY_ERR exception (<http://www.w3.org/TR/2007/WD-XMLHttpRequest-20070618/#dfn-open>).
BR, Julian
