    def prepare(self, reactor, clock, hs):
        # build a replication server
        server_factory = ReplicationStreamProtocolFactory(hs)
        self.streamer = hs.get_replication_streamer()
        self.server = server_factory.buildProtocol(None)

        # Make a new HomeServer object for the worker
        self.reactor.lookups["testserv"] = "1.2.3.4"
        self.worker_hs = self.setup_test_homeserver(
            http_client=None,
            homeserver_to_use=GenericWorkerServer,
            config=self._get_worker_hs_config(),
            reactor=self.reactor,
        )

        # Since we use sqlite in memory databases we need to make sure the
        # databases objects are the same.
        self.worker_hs.get_datastore().db_pool = hs.get_datastore().db_pool

        self.test_handler = self._build_replication_data_handler()
        self.worker_hs._replication_data_handler = self.test_handler

        repl_handler = ReplicationCommandHandler(self.worker_hs)
        self.client = ClientReplicationStreamProtocol(
            self.worker_hs, "client", "test", clock, repl_handler,
        )

        self._client_transport = None
        self._server_transport = None
A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks.