RR",
                    function() { el.setAttributeNS(null, "aa:bb", "fail") })
}, "A namespace is required to use a prefix.")

// Step 5
test(function() {
  var el = document.createElement("foo")
  assert_throws_dom("NAMESPACE_ERR",
                    function() { el.setAttributeNS("a", "xml:bb", "fail") })
}, "The xml prefix should not be allowed for arbitrary namespaces")
test(function() {
  var el = document.createElement("foo")
  el.setAttributeNS(XML, "a:bb", "pass")
  assert_equals(el.attributes.l