Behat is a tool for having better conversations with your team about expectations for the software being built. By it’s nature, Behat separates the expectations (the steps written in feature files) from the implementation details (the PHP files that define the steps). This separation of concerns can make Behat both powerful and cumbersome. Once comfortable with Behat’s complexity, there is room for a lot of creative usage.
A great introduction to the topic for people new to Behat; worth about forty three minutes of your time. Slides available here.
Bonus: My Behat for WordPress extension (WordHat) makes a cameo around the 38:30 minutes mark.