def test_walksDownPath(self):
        """
        C{_qualNameWalker} is a generator that, when given a Python qualified
        name, yields that name, and then the parent of that name, and so forth,
        along with a list of the tried components, in a 2-tuple.
        """
        walkerResults = list(runner._qualNameWalker("walker.texas.ranger"))

        self.assertEqual(walkerResults,
                         [("walker.texas.ranger", []),
                          ("walker.texas", ["ranger"]),
                          ("walker", ["texas", "ranger"])])

        C{_qualNameWalker} is a generator that, when given a Python qualified
        name, yields that name, and then the parent of that name, and so forth,
        along with a list of the tried components, in a 2-tuple.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_runner.py