def test_suffix(self):
        """
        L{Tag.__call__} accepts Python keywords with a suffixed underscore as
        the DOM attribute of that literal suffix.
        """
        proto = Tag('div')
        tag = proto()
        tag(class_='a')
        self.assertEqual(tag.attributes, {'class': 'a'})

        L{Tag.__call__} accepts Python keywords with a suffixed underscore as
        the DOM attribute of that literal suffix.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_stan.py