Building Any System

From Curtis Poe, "Building Large Systems"...

Here’s a little secret that many “test-infected” developers know: testing makes you a better programmer. It’s not just that your code works. It’s that if you find something is hard to test, that’s a code smell. Maybe your superWunderFunction() which takes 13 arguments isn’t designed terribly well. That’s not saying that all hard-to-test code has a design flaw... but as you test more, you start writing code that’s easier to test...

When you start writing code that is easier to test, do you know what you’re doing? You’re eating your own dog food. You’re using your code and you start writing code which is easier to use. It starts becoming better-designed code. As an added benefit, if programmers are unsure how to use your code, they can always read the tests. Tests are not a substitute for documentation, but they are an excellent supplement to it.