Tag Archives: mocks

Does stubbing make your tests brittle?

Stubbing and mocking in unit tests is generally considered a Good Thing. It can make your tests run faster, it helps you not to cross boundaries. But it also makes your tests more brittle.

The reason for this is simple. If you want to stub out some method, you have to do it very precisely. You have to know the underlying implementation and choose a very concrete instance and method for stubbing. This makes your test very tightly coupled to the implementation details of tested class. And tightly coupled is brittle. Let’s look at some trivial example:

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