TDD

Does test-driven development work with legacy applications? That is a question I get a lot, and the short answer is yes. In this video I take a big, ugly WinForms application and walk through how I use TDD to add a new feature without touching the messy parts of the existing code. The goal is simple: show that the test-first mindset works even when the surrounding codebase has no tests at all.

What exactly is TDD or Test-Driven Development, and why do so many experienced engineers swear by it? In this short video I explain where TDD comes from, how the red-green-refactor cycle works, and I walk through a simple C# calculator example that shows the process in action. TDD is not only a development technique, it is a mindset that shapes how you approach every line of code.