def test_requestService(self):
        """
        Test that requesting a service sends a SERVICE_REQUEST packet.
        """
        self.proto.requestService(MockService())
        self.assertEqual(self.packets, [(transport.MSG_SERVICE_REQUEST,
                                         b'\x00\x00\x00\x0bMockService')])

        Test that requesting a service sends a SERVICE_REQUEST packet.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_transport.py