def test_defaultTTYFilename(self):
        """
        If not passed the name of a tty in the filesystem,
        L{_NewConnectionHelper} uses C{b"/dev/tty"}.
        """
        helper = _NewConnectionHelper(
            None, None, None, None, None, None, None, None, None, None)
        self.assertEqual(FilePath(b"/dev/tty"), helper.tty)

        If not passed the name of a tty in the filesystem,
        L{_NewConnectionHelper} uses C{b"/dev/tty"}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_endpoints.py