Apex Developer Guide
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Testing Asynchronous Callouts
The following example shows how to invoke a mock asynchronous callout in a test for a Web service call that uses HTTPRequest. To simulate callouts in continuations, call these methods of the Test class: Test.setContinuationResponse() and Test.invokeContinuationMethod().
The controller class to test is listed first, followed by the test class. The controller class from Make Long-Running Callouts with Continuations is reused here.
public with sharing class ContinuationController {
// Unique label corresponding to the continuation request
public String requestLabel;
// Result of callout
public String result {get;set;}
// Endpoint of long-running service
private static final String LONG_RUNNING_SERVICE_URL =
'<Insert your service URL>';
// Action method
public Object startRequest() {
// Create continuation with a timeout
Continuation con = new Continuation(40);
// Set callback method
con.continuationMethod='processResponse';
// Create callout request
HttpRequest req = new HttpRequest();
req.setMethod('GET');
req.setEndpoint(LONG_RUNNING_SERVICE_URL);
// Add callout request to continuation
this.requestLabel = con.addHttpRequest(req);
// Return the continuation
return con;
}
// Callback method
public Object processResponse() {
// Get the response by using the unique label
HttpResponse response = Continuation.getResponse(this.requestLabel);
// Set the result variable that is displayed on the Visualforce page
this.result = response.getBody();
// Return null to re-render the original Visualforce page
return null;
}
}This example shows the test class corresponding to the controller. This test class contains a test method for testing an asynchronous callout. In the test method, Test.setContinuationResponse sets a mock response, and Test.invokeContinuationMethod causes the callback method for the continuation to be executed. The test ensures that the callback method processed the mock response by verifying that the controller’s result variable is set to the expected response.
@isTest
public class ContinuationTestingForHttpRequest {
public static testmethod void testWebService() {
ContinuationController controller = new ContinuationController();
// Invoke the continuation by calling the action method
Continuation conti = (Continuation)controller.startRequest();
// Verify that the continuation has the proper requests
Map<String, HttpRequest> requests = conti.getRequests();
system.assert(requests.size() == 1);
system.assert(requests.get(controller.requestLabel) != null);
// Perform mock callout
// (i.e. skip the callout and call the callback method)
HttpResponse response = new HttpResponse();
response.setBody('Mock response body');
// Set the fake response for the continuation
Test.setContinuationResponse(controller.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 body', controller.result);
}
}