Function Programming and Mock Objects

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I was recently watching a webcast on Clojure. In it the presenter made a comment in the context of discussing the FP nature of Clojure which went something like (I hope I don't misrepresent him) "Mock objects are mocking you".

I also heard a similar comment a while back when I watched a webcast when Microsoft's Reactive Framework was starting to appear . It went something like "Mock objects are for those who don't know math")

Now I know that both comments are jokes/tongue-in-cheek etc etc (and probably badly paraphrased), but underlying them is obviously something conceptual which I don't understand as I haven't really made the shift to the FP paradigm.

So, I would be grateful if someone could explain whether FP does in fact render mocking redundant and if so how.

mocking functional-programming
2 Answers

I think the important thing to think about is the idea of using tests help you to structure your code. Mocks are really about deferring decisions you don't want to take now (and a widely misunderstood technique). Instead of object state, consider partial functions. You can write a function that takes defers part of its behaviour to a partial function that's passed in. In a unit test, that could be a fake implementation that lets you just focus on the code in hand. Later, you compose your new code with a real implementation to build the system.

Actually, when we were developing the idea of Mocks, I always thought of Mocks this way. The object part was incidental.

user_751230
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