def test_sslWithDefaults(self):
        """
        When passed an SSL strports description without extra arguments,
        L{clientFromString} returns a L{SSL4ClientEndpoint} instance
        whose context factory is initialized with default values.
        """
        reactor = object()
        client = endpoints.clientFromString(reactor, "ssl:example.net:4321")
        self.assertIsInstance(client, endpoints.SSL4ClientEndpoint)
        self.assertIs(client._reactor, reactor)
        self.assertEqual(client._host, "example.net")
        self.assertEqual(client._port, 4321)
        certOptions = client._sslContextFactory
        self.assertEqual(certOptions.method, SSLv23_METHOD)
        self.assertIsNone(certOptions.certificate)
        self.assertIsNone(certOptions.privateKey)

        When passed an SSL strports description without extra arguments,
        L{clientFromString} returns a L{SSL4ClientEndpoint} instance
        whose context factory is initialized with default values.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_endpoints.py