It's possible that you've had some exposure to unit tests in your career. It's highly likely that you've written a test or two. Many developers, unfortunately, haven't had the opportunity to experience the joys of Test-Driven Development.
First, a little background
John's story on TDD
I was first introduced to TDD about five years ago. I was interviewing for a lead developer position for a small startup. During the interview process, the CTO mentioned that the development team was practicing TDD. I informed him that I didn't have any practical TDD experience, but that I was sure I could adapt.
In all honesty, I was bit nervous. Up to that point, I had never even written a single unit test! What had I gotten myself into? An offer was extended and I accepted. Once I joined the small company I was told that, while TDD was the goal, they weren't quite there yet. Phew; crisis averted. However, I was still intrigued. It wasn't until a few months later that the team delved into the world of TDD, and the rest, as they say, is history.
Clayton's story on TDD
My introduction to TDD is a little different from John's. I have been writing code since I was in middle school in the early 1990s. From then until 2010, I always struggled with writing applications that didn't require serious architectural changes when new requirements were introduced. In 2010, I finally got fed up with the constant rewrites and began researching tools and techniques to help me with my problem. I quickly found TekPub, an e-learning site that was, at the time, owned and operated by Rob Conery. Through TekPub I began learning the SOLID principles and TDD. After banging my head against the wall for close to six months, I started to grasp what TDD was and how I could use those principles. Coupled with the SOLID principles, TDD helped me to write easy to understand code that was flexible enough to stand up to any requirements the business could throw at me. I eventually ended up at the same company where John was employed and worked with him and, as he said, the rest is history.
The SOLID principles, which will be explained in detail later, are guiding principles that help produce clean, maintainable, and flexible code. They help reduce rigidity, fragility, and complexity. Generally thought of as object-oriented principles, I have found them to be applicable in all coding paradigms.
