I'm currently working on covering code coverage for continuation pattern. However, I receive an exception while testing. I have chained 3 webservices ie., service 1,2 and 3.

 private static testMethod void testContinuation1() {
 setAllData();// test data is set up here
  MainController Controller = new MainController();

    // Invoke the continuation by calling the action method
    Continuation conti = (Continuation)Controller.CallMainMethod();

    Map<String, HttpRequest> requests = conti.getRequests();

    HttpResponse response = new HttpResponse();
    HttpRequest request = new HttpRequest();

    for(String RequestLabel: requests.keyset()){
        request = requests.get(RequestLabel);
        if(request.getEndpoint().contains('Service1')) {
        else if(request.getEndpoint().contains('Service2')) {
        Test.setContinuationResponse(RequestLabel, response);                   
    system.assert(requests.size() == 3);

    if(conti != null){
      Object result = Test.invokeContinuationMethod(Controller, conti);

I'm not able to set the mock responses for each webservices. Rather, I receive an error as..

Argument 2 cannot be null.

in Test.invokeContinuationMethod. Also debug 'conti-->' has a callback method. Do I have to instantiate 3 different Continuation object to test 3 different webservices?

Suggestion would be appreciated. Thanks!


You don't have to instantiate 3 different Continuation objects to test 3 different webservices.

Only single instance of Continuation object will work.

I have tried to replicate your use case using Continuation creating multiple callouts

Controller (taken from Making Multiple Asynchronous Callouts)

public with sharing class MultipleCalloutController {

    // Unique label for the first request
    public String requestLabel1;
    // Unique label for the second request
    public String requestLabel2;
    // Result of first callout
    public String result1 {get;set;}
   // Result of second callout
    public String result2 {get;set;}
    // Endpoints of long-running service
    private static final String LONG_RUNNING_SERVICE_URL1 = 
        '<Insert your first service URL>';
    private static final String LONG_RUNNING_SERVICE_URL2 = 
        '<Insert your second service URL>';

    // Action method
    public Object startRequestsInParallel() {
      // Create continuation with a timeout
      Continuation con = new Continuation(60);
      // Set callback method

      // Create first callout request
      HttpRequest req1 = new HttpRequest();

      // Add first callout request to continuation
      this.requestLabel1 = con.addHttpRequest(req1);     

      // Create second callout request
      HttpRequest req2 = new HttpRequest();

      // Add second callout request to continuation
      this.requestLabel2 = con.addHttpRequest(req2);     

      // Return the continuation
      return con;  

    // Callback method.
    // Invoked only when responses of all callouts are returned.
    public Object processAllResponses() {   
      // Get the response of the first request
      HttpResponse response1 = Continuation.getResponse(this.requestLabel1);
      this.result1 = response1.getBody();

      // Get the response of the second request
      HttpResponse response2 = Continuation.getResponse(this.requestLabel2);
      this.result2 = response2.getBody();

      // Return null to re-render the original Visualforce page
      return null;

Test Class

public class MyContinuationTesting {
    public static testmethod void testWebService() {
        MultipleCalloutController controller = new MultipleCalloutController();
        // Invoke the continuation by calling the action method
        Continuation conti = (Continuation)controller.startRequestsInParallel();

        // Verify that the continuation has the proper requests
        Map<string, System.HttpRequest> requests = conti.getRequests();

        system.assert(requests.size() == 2);
        system.assert(requests.get(controller.requestLabel1) != null);

        // Perform mock callout 
        // (i.e. skip the callout and call the callback method)
        integer i = 1;
        for(String RequestLabel: requests.keyset())
            HttpResponse response = new HttpResponse();
            response.setBody('Mock response body' + i); 
            Test.setContinuationResponse(RequestLabel, response);
        // Invoke callback method
        Object result = Test.invokeContinuationMethod(controller, conti);
        // result is the return value of the callback
        System.assertEquals(null, result);
        // Verify that the controller's result variable
        //   is set to the mock response.
        System.assertEquals('Mock response body1', controller.result1);

        System.assertEquals('Mock response body2', controller.result2);
  • Hi @santanu is the controller class covered by this test class? Because I too tried with the "i" variable and it didn't work as I won't know which service would be of which label. – MnZ May 21 '17 at 1:25
  • Are you getting the error which you were getting earlier? – Santanu Boral May 21 '17 at 1:47
  • I'm trying it out again. I will reply once I'm done – MnZ May 21 '17 at 1:49
  • So basically all the assert statements failed." I get this error--> External entry point Class.System.Test.invokeContinuationMethod" .The request labels for service1 and service2 are in 2 separate classes. – MnZ May 21 '17 at 2:29
  • I can't see your controller code so can't predict that, but the code example I have given is perfectly working for me – Santanu Boral May 21 '17 at 2:32

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