DEV Community

loading...

Discussion on: Unit Testing is Overrated

Collapse
mirichan profile image
Mirichan

You mention in a comment that these problems are largely with mocks and that mocks are often necessary.

That's where this all falls down. Mocks are only as necessary as your application design makes them. I can't remember the last time I had to mock something in a codebase I've had reasonable influence over.

If you embrace referential transparency and push side effects to modules at the edge of your application and use interfaces to test them, you just don't need mocks. The only thing you need then is a few integration tests to ensure that the effectful code at the edges interacts with the real world correctly.

Collapse
tyrrrz profile image
Alexey Golub Author

This was shown in the article. Unfortunately, separating pure from impure code will be able to get you so far and you will still have to mock quite a few things. For example, think of a case where you need to query a small portion of a very big dataset, then perform some transformation on it, then use the result to query another portion, transform that one, and finally post the resulting data to some web service. Your pure code is interleaved with impure code and your best option is to test those parts separately, but that breaks the flow in which the code is executed and you won't have confidence that you tested the pure parts exhaustively, or in the fact that the side-effects are executed correctly. This approach works out for simple transformations that follow the [data in] -> [data out] principle, but unfortunately that's not always the case.

Collapse
mirichan profile image
Mirichan

Wow. Look, I don't doubt that this has been true for you, but you can't speak in absolutes like that and not expect opposition.

You're speaking from an experience informed by the codebases you've worked in. I assure you that there are other codebases out there for which your statements are categorically untrue.