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

I'd say you need mainly two things to test, and they go hand in hand:

• Interfaces, interfaces, interfaces
• dependency injection; this in conjunction with interfaces will help you swap parts at will to isolate the modules you want to test. You want to test your cron-like system that sends notifications to other services? instanciate it and substitute your real-code implementation for everything else by components obeying the correct interface but hard-wired to react in the way you want to test: mail notification? test what happens when the smtp server is down by throwing an exception

I myself haven't mastered the art of unit testing (and i'm far from it), but this is where my main efforts are going currently. The problem is that i still don't design for tests, and as a result my code has to bend backwards to accomodate...