The createAttributeNS of Document Interface is supposed to throw an exception NAMESPACE_ERR if the qualifiedName has a prefix that is "xml" and the namespaceURI is neither null nor an empty string nor http://www.w3.org/XML/1998/namespace",
or if the qualifiedName has a prefix that is "xmlns" but the namespaceURI is neither null nor an empty string.
Howeer it sucessfully passes the test and does not throw this exception.