[lkitching]

> that method is now dependent on the static class and you don't have any control over it.

I don't see how you have any less control over it than any other code you wrote. If you don't want it to write log statements, then don't do that. Most static methods are small and pure so don't need to write log statements anyway.

> Now your testing will dirty whatever database you're using, as well as run 10x slower.

I've never used a logging framework that didn't allow you to configure where log statements were written, or give you control over the logging threshold for individual classes. However if your method is writing logs then presumably there is a reason, which is just as useful in the tests. If you mock it out then you're testing against different code to the one you will actually run against.

> If you start using a custom delegate solution, then your code is not consistent with everything else that uses DI.

Passing functions as arguments directly is 'DI', just without the need to configure that through an external container. Reducing the amount of interfaces (often with a single implementation) and external configuration makes navigating the code easier.

[hacker_9]

I think you missed my point, it's not about the logging framework, its about the fact you don't control an external dependency during testing. Unit tests are meant to be reproducible, meaning they are done under controlled conditions.

> Most static methods are small and pure

This is very assuming, tests are a way of being specific about your intent.

[lkitching]

> its about the fact you don't control an external dependency during testing

If your code is structured using small static functions, you don't have any dependencies in the first place, just arguments you are passed and transform. You will probably create interfaces for external services you depend on, but you can avoid needing to mock them if you express the transform directly.

> This is very assuming

I'm not assuming anything, since I wrote the static method and I also decided to call it, presumably for the result it calculates. Your argument appears to be that static methods could contain bad code but that applies to all code you depend on.