:lang, xml:lang vs. lang
Ignore this test. (:lang with xml:lang is not supported)
You can only get meaningful results for this test if :lang works with both lang and xml:lang attributes.
Test passes if you see green below.
Assertion: When an xml:lang attribute and a lang attribute on the same element have different values, the xml:lang value will match :lang for pages served as application/xhtml+xml.