When mocking a class with Moq, how can I CallBase for just specific methods?

Question

I really appreciate Moq\'s Loose mocking behaviour that returns default values when no expectations are set. It\'s convenient and saves me code, and it also act

Answer 1

Since nobody's answered this question for ages and I think it deserves an answer, I'm going to focus on the highest-level question you asked: how to keep these benefits when the method under test happens to be virtual.

Quick answer: you can't do it with Moq, or at least not directly. But, you can do it.

Let's say that you have two aspects of behaviour, where aspect A is virtual and aspect B is not. That pretty much mirrors what you've got in your class. B can use other methods or not; it's up to you.

At the moment, your class Foo is doing two things - both A and B. I can tell that they're separate responsibilities just because you want to mock A out and test B on its own.

Instead of trying to mock out the virtual method without mocking out anything else, you can:

• move behaviour A into a separate class
• dependency inject the new class with A into Foo through Foo's constructor
• invoke that class from B.

Now you can mock A, and still call the real code for B..N without actually invoking the real A. You can either keep A virtual or access it through an interface and mock that. This is in line with the Single Responsibility Principle, too.

You can cascade constructors with Foo - make the constructor Foo() call the constructor Foo(new A()) - so you don't even need a dependency injection framework to do this.

Hope this helps!