return nil, err
		}
		responses = append(responses, resp)
		return responses, nil
	}

	return responses, nil
}

func mergeShards(responses map[string]*discovery.DiscoveryResponse) (*discovery.DiscoveryResponse, error) {
	retval := discovery.DiscoveryResponse{}
	if len(responses) == 0 {
		return &retval, nil
	}

	for _, response := range responses {

			staticCluster: "",
			updateCluster: "",
		},
	})

	// Expect that we send an EDS response even though there was no request
	resp := ads.ExpectResponse()
	if resp.TypeUrl != v3.EndpointType {
		t.Fatalf("unexpected response type %v. Expected dependent EDS response", resp.TypeUrl)
	}
	// we must NOT get the cluster back

	// TCP settings.
	TCP TCP

	// TLS settings.
	TLS TLS

	// HBONE settings.
	HBONE HBONE

	// Message to be sent.
	Message string

	// Check the server responses. If none is provided, only the number of responses received
	// will be checked.
	Check Checker

	// If we have been asked to do TCP comms with a PROXY protocol header,
	// determine which version (1 or 2), and send the header.

	if notExpected > 0 {
		notExpectedStr = strconv.Itoa(notExpected)
	}
	return func(r echoClient.Response) error {
		if r.Code == notExpectedStr {
			return fmt.Errorf("received unexpected response code `%s`. Response: %s", notExpectedStr, r)
		}
		return nil
	}
}

// GRPCStatus checks that the gRPC response status code matches the expected value.
func GRPCStatus(expected codes.Code) echo.Checker {

		case resp := <-con.deltaResponsesChan:
			// TODO: separate upstream response handling from requests sending, which are both time costly
			proxyLog.WithLabels(
				"id", con.conID,
				"type", model.GetShortType(resp.TypeUrl),
				"nonce", resp.Nonce,
				"resources", len(resp.Resources),
				"removes", len(resp.RemovedResources),
			).Debugf("upstream response")
			metrics.XdsProxyResponses.Increment()

		},
		{
			// This is not a NXDOMAIN, but empty response
			name: "success: Error response if only AAAA records exist for typeA",
			host: "ipv6.localhost.",
		},
		{
			// This is not a NXDOMAIN, but empty response
			name:      "success: Error response if only A records exist for typeAAAA",
			host:      "ipv4.localhost.",
			queryAAAA: true,
		},
		{

// (right now calls it from initDiscoveryService in pkg/bootstrap/server.go).
func (r *JwksResolver) Close() {
	closeChan <- true
}

// Compare two JWKS responses, returning true if there is a difference and false otherwise
func compareJWKSResponse(oldKeyString string, newKeyString string) (bool, error) {
	if oldKeyString == newKeyString {
		return false, nil
	}

		HTTP: echo.HTTP{
			Path: "/" + testName,
		},
	})
	if err != nil {
		return fmt.Errorf("failed to request to external service: %s", err)
	}
	if res.Responses[0].Code != "200" {
		return fmt.Errorf("expected to get 200 status code, got: %s", res.Responses[0].Code)
	}
	return nil
}

func verifyThatRequestWasTunneled(target echo.Instance, expectedSourceIPs []corev1.PodIP, expectedPath string) error {

	}
}

// sendDownstream sends discovery response.
func sendDownstream(downstream adsStream, response *discovery.DiscoveryResponse) error {
	tStart := time.Now()
	defer func() {
		// This is a hint to help debug slow responses.
		if time.Since(tStart) > 10*time.Second {
			proxyLog.Warnf("sendDownstream took %v", time.Since(tStart))
		}
	}()
	return downstream.Send(response)
}

func (p *XdsProxy) close() {

	if lp == nil {
		if h.respondBeforeSync {
			response = h.upstream(proxy, req, hostname)
			response.Truncate(size(proxy.protocol, req))
			_ = w.WriteMsg(response)
		} else {
			log.Debugf("dns request for host %q before lookup table is loaded", hostname)
			response = new(dns.Msg)
			response.SetReply(req)
			response.Rcode = dns.RcodeServerFailure
			_ = w.WriteMsg(response)
		}
		return
	}