Useful design patterns for unit testing/TDD?

Question

Reading this question has helped me solidify some of the problems I\'ve always had with unit-testing, TDD, et al.

Since coming across the TDD approach to development I k

Answer 1

have made me realise that the next step is understanding how to de-couple code to make it testable.

What should I be looking at to help me do this? Is there a specific set of design patterns that I need to understand and start to implement which will allow easier testing?

Right on! SOLID is what you are looking for (yes, really). I keep recommending these 2 ebooks, specially the one on SOLID for the issue at hand.

You also have to understand that its very hard if you are introducing unit testing to an existing code base. Unfortunately tightly coupled code is far too common. This doesn't mean not to do it, but for a good time it'll be just like you mentioned, tests will be more concentrated in small pieces.

Over time these grow into a larger scope, but it does depend on the size of the existing code base, the size of the team and how many are actually doing it instead of adding to the problem.