How to Mock the Internal Method of a class ?

Question

I have a class which has a internal method and i want to mock the internal method . But i am unable to mock it i.e. it is not calling the mocked function but calling the original function. Is there any way to achieve this ?

Edit:Actually i am a novice to the Moq. I have many classes and methods of the classes to test using the Moq. Many classes are internal , many have internal methods, many have not-virtual methods . And can not change the signature on the methods and classes. Can anyone please let me know how to go about testing this scenario using Moq. Or else please suggest me some other testing framework which is easy to learn and easy to work with .

Answer 1

Why would you want to mock an internal method?

If you find the need to mock an internal method, say to sidestep a dependency or an interaction, you perhaps should consider redesign of the class.

Inversion of Control and Dependency Injection are some possible design strategies that can reduce coupling and increase cohesion of your classes and eliminate the need to mock internal methods.

I don't believe there is a clear path to non-public mocking with Moq.

But, if you absolutely must, you can use TypeMock Isolator to mock just about anything.

Also, just so it doesn't get lost in the din: Thomas linked a good article on using the free MS Moles to mock non-public members.

Mocking the Unmockable: Using Microsoft Moles with Gallio

Answer 2

Unit testing should test the interface of a class. You can mock out dependencies, but implementation details of the class itself (such as private methods) should be tested as part of the whole class, not separately, and not changed for the test (otherwise you would be testing a different unit then would really be used).

If you feel it is necessary to change the method to make the class testable, refactor the class so that the difficult part becomes a dependency, or otherwise substitutable by parameter or subclassing.

Answer 3

Not with Moq.

But you can use the free Moles framework from MS to do such things. I wrote about it here: Mocking the Unmockable: Using Microsoft Moles with Gallio. (it applies not only to Gallio, but it gives a good overall impression of what you can do with Moles...). The other alternative would be Typemock...

HTH. Thomas

Answer 4

If you need to test lots of code that you can't change, you should better go with MS Moles or TypeMock from the beginning.

Free mocking frameworks like Moq give you only support on interfaces and virtual methods anyway. Does not sound as if you will go far with that...

Thomas

Answer 5

You can easily mock a internal virtual methods by adding the following to your AssemblyInfo.cs:

[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2")] // namespace in Moq
[assembly: InternalsVisibleTo("YourTestClass")]

I'm not a unit testing expert, but I don't understand why other answers are saying you should never do it? Isn't that what you do when you use the 'Extract and Override' (local factory method) dependency injection technique outlined by Roy Osherove in Chapter 3 of The Art Of Unit Testing?

Answer 6

Mark the method as internal *protected* (also virtual of course)