Should every single object have an interface and all objects loosely coupled?

Question

From what I have read best practice is to have classes based on an interface and loosely couple the objects, in order to help code re-use and unit test.

Is this corr

Answer 1

It's useful for objects which really provide a service - authentication, storage etc. For simple types which don't have any further dependencies, and where there are never going to be any alternative implementations, I think it's okay to use the concrete types.

If you go overboard with this kind of thing, you end up spending a lot of time mocking/stubbing everything in the world - which can often end up creating brittle tests.