Testing is the last leg in your journey to Rails development greatness. With tests, you know you can build apps faster, confidently add new features without breaking old ones, and debug much more efficiently. You might even know how to test with all the great tools and frameworks out there. Your problem is that you just don't know what to test.
A good introduction to Rails application testing. The author uses realistic examples and a quirky sense of humor to get the reader past and concerns or reservations and into the habit of producing well-tested code.