In this article, I’d like to discuss the differences in using stubs and mocks and show how you can abandon using mocks even in the cases where you need to verify that objects interact with each other correctly.

In the previous articles, we discussed what causes the pain while writing unit tests (mocks), and how to make TDD painless (get rid of the mocks). Today, I want to set the groundwork and discuss why mocks actually cause so much pain to us, developers.

Unit testing is good at checking the correctness of your code in isolation, but it’s not a panacea. Only integration tests can give us confidence that the application we develop actually works as a whole. They are also a good substitute for mocks in the cases where you can’t test important business logic without involving external dependencies.

Last week, we nailed the root cause of the problems, related to so-called test-induced damage - damage we have to bring into our design in order to make the code testable. Today, we’ll look at how we can mitigate that damage, or, in other words, do painless TDD.

I’m going to write a couple of posts on the topic of TDD. Over the years, I’ve come to some conclusions of how to apply TDD practices and write tests in general that I hope you will find helpful. I’ll try to distil my experience with it to several points which I’ll illustrate with examples.