    def test_federation_client_unsafe_ip(self, resolver):
        self.sydent.run()

        request, channel = make_request(
            self.sydent.reactor,
            "POST",
            "/_matrix/identity/v2/account/register",
            {
                "access_token": "foo",
                "expires_in": 300,
                "matrix_server_name": "example.com",
                "token_type": "Bearer",
            },
        )

        resolver.return_value = defer.succeed(
            [
                Server(
                    host=self.unsafe_domain,
                    port=443,
                    priority=1,
                    weight=1,
                    expires=100,
                )
            ]
        )

        request.render(self.sydent.servlets.registerServlet)

        self.assertNot(self.reactor.tcpClients)

        self.assertEqual(channel.code, 500)
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.