def test_sslPositionalArgs(self):
        """
        When passed an SSL strports description, L{clientFromString} returns a
        L{SSL4ClientEndpoint} instance initialized with the values from the
        string.
        """
        reactor = object()
        client = endpoints.clientFromString(
            reactor,
            "ssl:example.net:4321:privateKey=%s:"
            "certKey=%s:bindAddress=10.0.0.3:timeout=3:caCertsDir=%s" %
            (escapedPEMPathName, escapedPEMPathName, escapedCAsPathName))
        self.assertIsInstance(client, endpoints.SSL4ClientEndpoint)
        self.assertIs(client._reactor, reactor)
        self.assertEqual(client._host, "example.net")
        self.assertEqual(client._port, 4321)
        self.assertEqual(client._timeout, 3)
        self.assertEqual(client._bindAddress, ("10.0.0.3", 0))

        When passed an SSL strports description, L{clientFromString} returns a
        L{SSL4ClientEndpoint} instance initialized with the values from the
        string.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_endpoints.py