def _test(self, d, send, recv, result):
        """
        Implementation of C{_test} which checks that the command sends C{send}
        data, and that upon reception of C{recv} the result is C{result}.

        @param d: the resulting deferred from the memcache command.
        @type d: C{Deferred}

        @param send: the expected data to be sent.
        @type send: C{bytes}

        @param recv: the data to simulate as reception.
        @type recv: C{bytes}

        @param result: the expected result.
        @type result: C{any}
        """
        def cb(res):
            self.assertEqual(res, result)
        self.assertEqual(self.transport.value(), send)
        d.addCallback(cb)
        self.proto.dataReceived(recv)
        return d

        Implementation of C{_test} which checks that the command sends C{send}
        data, and that upon reception of C{recv} the result is C{result}.

        @param d: the resulting deferred from the memcache command.
        @type d: C{Deferred}

        @param send: the expected data to be sent.
        @type send: C{bytes}

        @param recv: the data to simulate as reception.
        @type recv: C{bytes}

        @param result: the expected result.
        @type result: C{any}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_memcache.py