def test_pauseProducingInConnectionMade(self):
        """
        In C{connectionMade} of a client protocol, C{pauseProducing} used to be
        ignored: this test is here to ensure it's not ignored.
        """
        server = MyServerFactory()

        client = MyClientFactory()
        client.protocolConnectionMade = defer.Deferred()

        port = reactor.listenTCP(0, server, interface='127.0.0.1')
        self.addCleanup(port.stopListening)

        connector = reactor.connectTCP(
            port.getHost().host, port.getHost().port, client)
        self.addCleanup(connector.disconnect)

        def checkInConnectionMade(proto):
            tr = proto.transport
            # The transport should already be monitored
            self.assertIn(tr, reactor.getReaders() +
                              reactor.getWriters())
            proto.transport.pauseProducing()
            self.assertNotIn(tr, reactor.getReaders() +
                                 reactor.getWriters())
            d = defer.Deferred()
            d.addCallback(checkAfterConnectionMade)
            reactor.callLater(0, d.callback, proto)
            return d
        def checkAfterConnectionMade(proto):
            tr = proto.transport
            # The transport should still not be monitored
            self.assertNotIn(tr, reactor.getReaders() +
                                 reactor.getWriters())
        client.protocolConnectionMade.addCallback(checkInConnectionMade)
        return client.protocolConnectionMade

        In C{connectionMade} of a client protocol, C{pauseProducing} used to be
        ignored: this test is here to ensure it's not ignored.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_tcp.py