Test a catch block for callout exception

Question

I want to create a callout exception in test class for covering batch apex callout. I am able to cover the try block but can't get, how to cover the catch block. Can i hardcode or put something like this CalloutException excpObj with some particular exception so that the control enters the catch block??

for (Contact cont : scope){
    try {
         XXXXXXXX
    } catch (CalloutException excpObj) {
         some_method_name(cont.Id,' Callout Exception','---- ERROR = ' + excpObj.getMessage(),cont);
    }
}

Answer 1

There is exactly one way to do this.

Scaffold a System.CalloutException in your mock:

@TestVisible class UnauthorizedEndpointResponse implements HttpCalloutMock {
    public HttpResponse respond(HttpRequest request) {
        CalloutException e = (CalloutException)CalloutException.class.newInstance();
        e.setMessage('Unauthorized endpoint, please check Setup->Security->Remote site settings.');
        throw e;
    }
}

Then cause it to appear in your test with the normal HTTP mocks:

Test.setMock(HttpCalloutMock.class, new UnauthorizedEndpointResponse());
BatchClass.doTheCallout();

Answer 2

In addition to @regal's response, often you want to test what happens if you get a httpResponse status other than 200. Here is a code sample showing how to do that. You use arguments in the constructor of the Mock object to guide how the respond() method generates the response to the rest of your code.

The Mock class

public class myMock implements HttpCalloutMock {  
  Boolean  isMockResponseSuccessful;  // set by constructor, used to vary the mockresponse

  public myMock(Boolean isMockResponseSuccessful) {
    this.isMockResponseSuccessful  = isMockResponseSuccessful;
  }

  public HttpResponse respond(HttpRequest rqst) {
    HttpResponse hResp    = new HttpResponse();
    if (this.isMockResponseSuccessful) {
      hResp.setStatusCode(200);
      hResp.setBody(someJsonSuccessresponse);      
    }
    else {
      hResp.setStatusCode(400);
      hResp.setStatus('Bad request');
    }
    return hResp;
  }
}

The testmethods

private static void someTestmethodSuccess() {
  Test.startTest();
  Test.setMock(HttpCalloutMock.class, new myMock(true));  // mock with response = 200
  executeMymethod();
  System.assert(assertSomethingWhenExpectingSuccess);
  Test.stoptest();
}

private static void someTestmethodFailure() {
  Test.startTest();
  Test.setMock(HttpCalloutMock.class, new myMock(false));  // mock with response = 400
  executeMymethod();
  System.assert(assertSomethingWhenExpectingFailure);
  Test.stoptest();
}    

Answer 3

You can generate a callout exception this way:-

Try to perform a DML in between startTest() and stopTest();

It will generate:

System.CalloutException: You have uncommitted work pending. Please commit or rollback before calling out

public static testmethod void testConstructor()    {

       Test.setMock(HttpCalloutMock.class, new MockHttpResponseGenerator());
       Test.startTest();
           Account acc = new Account(Name='Test Ignore'); // any sobject for DML
           insert acc;
           /* Replace me with execute batch statement here in between DML */
           delete acc;
       Test.stopTest();
 }

Basically, you need to do a DML before calling out. And it should be in same transaction.

Or you can use Test.isRunningTest() in batch class to perform DML.