Tests - one class and many methods or many classes - few methods?

Question

Software testing

I can't figure out how best to create tests.
Let's say I need to test the functionality of the application with some model.
Do I need to make a ModelTest.php test and it has a lot of methods, or is it better to separate classes and make it like UserObserverTest, UserRepositoryTest, UserMiddlewareTest and so on?

Answer 1

The second option is better - you do not need to collect everything in one heap.
So at least if you change UserRepository, you already know that you need to add / change theta in UserRepositoryTests