Mocking a method that takes a delegate in RhinoMocks

Question

I have the following classes:

public class HelperClass  
{  
    HandleFunction<T>(Func<T> func)
    {
         // Custom logic here

         func.Invoke();

         // Custom logic here  
}

// The class i want to test  
public class MainClass
{
    public readonly HelperClass _helper;

    // Ctor
    MainClass(HelperClass helper)
    {
          _helper = helper;
    }

    public void Foo()
    {
         // Use the handle method
         _helper.HandleFunction(() =>
        {
             // Foo logic here:
             Action1();
             Action2(); //etc..
        }
    }
}

I want to test MainClass only. I a using RhinoMocks to mock HelperClass in my tests.
The problem is, while I am not interested in testing the HandleFunction() method I am interested in checking Action1, Action2 and other actions that were sent to HandleFunction() when called..
How can I mock the HandleFunction() method and while avoiding it's inner logic, invoke the code that was sent to it as a parameter?

Answer 1

Because your unit under test most probably requires the delegate to be called before proceeding, you need to call it from the mock. There is still a difference between calling the real implementation of the helper class and the mock implementation. The mock does not include this "custom logic". (If you need that, don't mock it!)

IHelperClass helperMock = MockRepository.GenerateMock<IHelperClass>();
helperMock
  .Stub(x => x.HandleFunction<int>())
  .WhenCalled(call => 
  { 
    var handler = (Func<int>)call.Argument[0];
    handler.Invoke();
  });

// create unit under test, inject mock

unitUnderTest.Foo();

Answer 2

In addition to Stefan's answer I'd like to show quite another way to define stub which invokes passed argument:

handler
    .Stub(h => h.HandleFunction(Arg<Func<int>>.Is.Anything))
    .Do((Action<Func<int>>)(func => func()));

Please read more about Do() handler here and here.