Unit Testing Interfaces

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Why test an interface? Why not just test the concrete object(s) of that interface?

Posted 13-May-10 3:20am

N_tro_P

Updated 13-May-10 13:04pm

Moak

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Wes Aday · Answer 1 · 2010-05-13T03:31:00

Solution 1

IMO since interfaces do not contain any code, you should not waste time writing tests for them (what is there to test?), if you are talking about interfaces in C#. Test the classes that implement the interface and let it go at that.

Posted 13-May-10 3:31am

Wes Aday

Comments

[no name] 13-May-10 9:35am

That is what I believe also but a google search will result in discussions about using Mock objects.
Doesn't seem like there is a point though, as you said why not test the classes that impliment it.. Then you have it covered.
I just wanted to see if anyone knew something I was missing.

[no name] 13-May-10 16:00pm

I do not believe that Mocking an object is the same as testing an interface. Mocking is supplying the unit under test with a fake object so that you can proceed with testing an object without introducing possible bugs from another object. I do not see the two being the same thing at all. And yes it makes my eyes cross when I read it too.

Abhinav S · Answer 2 · 2010-05-13T07:59:00

Solution 2

Creating a mock object does not necessarily mean that the interface will be tested - a mock object is essentially 'acting as a proxy' for another object that may not be available during testing.

Posted 13-May-10 7:59am

Abhinav S