def test_createsList(self):
        """
        The C{--auth} command line creates a list in the
        Options instance and appends values to it.
        """
        options = DummyOptions()
        options.parseOptions(['--auth', 'memory'])
        self.assertEqual(len(options['credCheckers']), 1)
        options = DummyOptions()
        options.parseOptions(['--auth', 'memory', '--auth', 'memory'])
        self.assertEqual(len(options['credCheckers']), 2)

        The C{--auth} command line creates a list in the
        Options instance and appends values to it.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/test/test_strcred.py