Contract Testing Explained for Beginners

Let me paint a scene that will feel familiar if you've worked on any project with more than one moving part. It's a Friday afternoon. You and the backend team have been building a new feature for two weeks. Everything passes locally. The QA environment looks clean. You ship to production feeling good about it. Then your phone buzzes. The frontend is broken. Users are seeing blank screens where their profile data should be. You dig in, and after twenty minutes of confusion, you find it: the bac...