How to cover Catch block for triggerfactory in Test class?

Question

I am using TriggerFramework for implementing a trigger on case. When I started writing tests for this trigger, this catch statement isn't covered by the tests:

trigger CaseMain on Case (before insert, before update, after insert, after update) {
  try {
       TriggerFactory.createAndExecuteHandler(CaseHandler.class);     
  } catch(Exception ex) {
       MilestoneUtils.SendNotificationOnTriggerFailure('CaseMain', ex);
  }
}

The rest of the code is executed, but not the catch batch. I tried to insert a record which would throw a SoqlException, NullPointerException, or a DmlException, but none of these covered the code.

Answer 1

One approach that I've taken to solve this problem is to include an @testVisible, private static Boolean forceException.

The code for that would be placed inside of your trigger factory, and would look like this:

public class TriggerFactory{
    @testVisible
    private static forceException = false;

    // Custom exception classes seem to be good practice
    // Doesn't really need to do anything other than extend the standard
    //   exception class
    public TriggerFactoryException extends Exception{}

    public static createAndExecuteHandler(...){
        if(forceException){
            throw new TriggerFactoryException('Forced exception');
        }

        // existing code here

    }
}

Then, in a unit test method, you simply set TriggerFactory.forceException = true;, et voila, easy, guaranteed exception.