Behavior-driven development (BDD)

Viktor Farcic: You're big on BDD. Can you explain to us, for those who may not know, what it is?

Liz Keogh: BDD came about as a replacement for test-driven development (TDD). TDD wasn't really about testing, because anyone who's done TDD would say that you wrote the test before there was even any code. Essentially, you're not really testing anything; you're describing how the code you're about to write is going to work, why it's going to be valuable to you, while coming up with some examples of how you want to use it.

When we actually start thinking of them as just examples of behavior, that's class-level behavior. You would say, "Here's an example of how my class behaves." But then you've got your system: "Here's an example of how my system behaves, here's an example of my application in use," and we call those scenarios. It's the same. You take your...