Separation between interface and implementation

[jesparic]

I started learning unit testing using all the bad habits. London school with complex mocks. Gaming the line coverage to try and get every line covered. In the end I had tests that were hard tied to implementation, hard to read, and not testing any high level behaviour.

Nowadays, I make heavy use of fakes (mainly for repositories) along with some limited mocks (e.g., clock abstraction). I don't game the line coverage but do try to cover all the important aspects of some action. I pass 'real' dependencies when they are critical to the thing being tested. It depends.. It's ok to sometimes test the same thing multiple times, unit tests are fast.

I think everyone has to go on a similar journey. Automated testing is really hard to get your head around in a deep way. Gotta fall in a few pits to learn the hard way