Unit-testing with dependencies between tests

Question

How do you do unit testing when you have

• some general unit tests
• more sophisticated tests checking edge cases, depending on the general ones

Answer 1

Personally, I wouldn't worry about creating dependencies between unit tests. This sounds like a bit of a code smell to me. A few points:

• If a test fails, let the others fail to and get a good idea of the scale of the problem that the adverse code change made.
• Test failures should be the exception rather than the norm, so why waste effort and create dependencies when the vast majority of the time (hopefully!) no benefit is derived? If failures happen often, your problem is not with unit test dependencies but with frequent test failures.
• Unit tests should run really fast. If they are running slow, then focus your efforts on increasing the speed of these tests rather than preventing subsequent failures. Do this by decoupling your code more and using dependency injection or mocking.