This is why you test from the outside in: You first write an acceptance test where you just specify what goes in and what should come out. The error/failure mes

This is why you test from the outside in: You first write an acceptance test where you just specify what goes in and what should come out. The error/failure messages you get when running this test drive your design and tell you which components you should write next. The RSpec book is a pretty good introduction to this topic.