How to assert that an action was called

Question

I need to asset an action called by a mock component.

 public interface IDispatcher
    {
     void Invoke(Action action);
    }

    public interface IDial         


        

Answer 1

You are actually testing this line of code:

dispatcher.Invoke(() => dialogService.Prompt(message));

Your class calls the mock to invoke a method on another mock. This is normally simple, you just need to make sure that Invoke is called with the correct arguments. Unfortunately, the argument is a lambda and not so easy to evaluate. But fortunately, it is a call to the mock which makes it easy again: just call it and verify that the other mock had been called:

Action givenAction = null;
mockDipatcher
  .AssertWasCalled(x => x.Invoke(Arg.Is.Anything))
  // get the argument passed. There are other solutions to achive the same
  .WhenCalled(call => givenAction = (Action)call.Arguments[0]);

// evaluate if the given action is a call to the mocked DialogService   
// by calling it and verify that the mock had been called:
givenAction.Invoke();
mockDialogService.AssertWasCalled(x => x.Prompt(message));