def test_frameElementFilename(self):
        """
        The I{filename} renderer of L{_FrameElement} renders the filename
        associated with the frame object used to initialize the
        L{_FrameElement}.
        """
        element = _FrameElement(
            TagLoader(tags.span(render="filename")),
            self.frame)
        d = flattenString(None, element)
        d.addCallback(
            # __file__ differs depending on whether an up-to-date .pyc file
            # already existed.
            self.assertEqual,
            b"<span>" + networkString(__file__.rstrip('c')) + b"</span>")
        return d

        The I{filename} renderer of L{_FrameElement} renders the filename
        associated with the frame object used to initialize the
        L{_FrameElement}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_util.py