Yes, mocking too much is a problem. Perhaps the greatest benefit of unit tests is that they force you to write code that can be tested in isolation. In other words, your code becomes modular. When you mock the whole world around your objects, there is nothing that forces you to separate the parts. You end up with code where you can’t create anything in isolation – it is all tangled together. From a recent tweet by Bill Wake: ”It’s ironic – the more powerful the mocking framework, the less pressure you feel to improve your design.” (from http://henrikwarne.com/2014/02/19/5-unit-testing-mistakes/)
> From a recent tweet by Bill Wake: ”It’s ironic – the more powerful the mocking framework, the less pressure you feel to improve your design.”
This is exactly my sentiment. I would go even further, though, and say that "the more powerful the mocking framework, the more it discourages design improvements." If you have 50 or 60 references in your test to a mocked class of type A, and A turns out to no longer be needed, then the effort to get rid of it is higher than it otherwise would be.
