Artikel bagus dari jayfields. http://blog.jayfields.com/2009/02/thoughts-on-developer-testing.html
When asking how and what you should test, start by thinking about what the goal of your project is. Once you understand your goal, select the tests that will help you achieve your goal. Different goals will definitely warrant using different testing patterns. If you start using a specific testing pattern and it hurts, you're probably using a pattern you don't need, or you've implemented the pattern incorrectly. Remember, we're all still figuring this out, so there's not really patterns that are right; just patterns that are right in a given context.
