How to mock with static methods?

c# .net mocking interface static-methods
brien picture brien · Sep 30, 2008 · Viewed 41.4k times · Source

I'm new to mock objects, but I understand that I need to have my classes implement interfaces in order to mock them.

The problem I'm having is that in my data access layer, I want to have static methods, but I can't put a static method in an interface.

What's the best way around this? Should I just use instance methods (which seems wrong) or is there another solution?

Answer

Jon Skeet picture Jon Skeet · Sep 30, 2008

Yes, you use instance methods. Static methods basically say, "There is one way to accomplish this functionality - it's not polymorphic." Mocking relies on polymorphism.

Now, if your static methods logically don't care about what implementation you're using, they might be able to take the interfaces as parameters, or perhaps work without interacting with state at all - but otherwise you should be using instances (and probably dependency injection to wire everything together).

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