public override Task InitializeAsync()
        {
            var router = new RoutingMessageHandler();

            _upstreamTestServer = new TestServer(UpstreamBuilder);
            _proxyPort          = 81;

            var proxyBuilder = ProxyBuilder
                               .UseSetting("port", _proxyPort.ToString())
                               .ConfigureTestServices(services =>
            {
                services.AddProxy(c =>
                {
                    c.ConfigurePrimaryHttpMessageHandler(() => router);
                    c.ConfigureHttpClient(client => client.Timeout = TimeSpan.FromSeconds(1));
                });
            });

            _proxyTestServer = new TestServer(proxyBuilder);

            router.AddHandler(new Origin("localhost", _proxyPort), _upstreamTestServer.CreateHandler());

            return(Task.CompletedTask);
        }