def test_createsDictionary(self):
        """
        The C{--auth} command line creates a dictionary mapping supported
        interfaces to the list of credentials checkers that support it.
        """
        options = DummyOptions()
        options.parseOptions(['--auth', 'memory', '--auth', 'anonymous'])
        chd = options['credInterfaces']
        self.assertEqual(len(chd[credentials.IAnonymous]), 1)
        self.assertEqual(len(chd[credentials.IUsernamePassword]), 1)
        chdAnonymous = chd[credentials.IAnonymous][0]
        chdUserPass = chd[credentials.IUsernamePassword][0]
        self.assertTrue(checkers.ICredentialsChecker.providedBy(chdAnonymous))
        self.assertTrue(checkers.ICredentialsChecker.providedBy(chdUserPass))
        self.assertIn(credentials.IAnonymous,
                      chdAnonymous.credentialInterfaces)
        self.assertIn(credentials.IUsernamePassword,
                      chdUserPass.credentialInterfaces)

        The C{--auth} command line creates a dictionary mapping supported
        interfaces to the list of credentials checkers that support it.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/test/test_strcred.py