def test_selectParseResponse(self):
        """
        L{HTTPAuthSessionWrapper._selectParseHeader} returns a two-tuple giving
        the L{ICredentialFactory} to use to parse the header and a string
        containing the portion of the header which remains to be parsed.
        """
        basicAuthorization = b'Basic abcdef123456'
        self.assertEqual(
            self.wrapper._selectParseHeader(basicAuthorization),
            (None, None))
        factory = BasicCredentialFactory('example.com')
        self.credentialFactories.append(factory)
        self.assertEqual(
            self.wrapper._selectParseHeader(basicAuthorization),
            (factory, b'abcdef123456'))

        L{HTTPAuthSessionWrapper._selectParseHeader} returns a two-tuple giving
        the L{ICredentialFactory} to use to parse the header and a string
        containing the portion of the header which remains to be parsed.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_httpauth.py