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Comment by arcticbull

16 days ago

When you write tests with mocks you almost always at some point end up with tests that test your mocks lol, and tests that test that you wrote the tests you think you wrote -- not the software itself.

I’ve never been thrilled by tests that rely on mocking — it usually means you need to re-express your module interface boundary.

Mocks for me fall into the class of software I affectionately call “load-bearing paint.” It’s basically universally the wrong tool for any given job but that really doesn’t stop people. Putting in a data class or similar model object and a delegate is usually sufficient and a much better tool.

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arcticbull

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xienze  16 days ago

> It’s basically universally the wrong tool for any given job but that really doesn’t stop people.

I find mocks useful for testing conditions that are on the periphery and would be a decent amount of trouble to set up. For instance, if I have a REST controller that has a catch all for exceptions that maps everything to a 500 response, I want a test that will cause the DAO layer to throw an exception and test that the rest of the "real stack" will do the translation correctly. A mock is the easiest way to accomplish that.

  • chillpenguin  16 days ago

    I agree. I will mock 3rd party APIs sometimes so I can test that my system correctly handles failures. For example, what if I get a 500 response from the API? With my mock I can easily make that happen. If I was using the actual API, I would have no way of forcing a 500 to happen.

mehagar  16 days ago

I agree that if you need to write mocks, it's likely that your interfaces are poorly defined. This is one of the claimed benefits of test driven development - writing the tests first forces you to design the code in a way that cleanly separates modules so they can be tested.

  • UK-Al05  16 days ago

    You have to mock/fake when modules call dependencies.

    Your way means you only ever have siblings. With an orchestrator pulling results out of one module and pushing it into another.