TDD is a “test-first” technique to develop and design software. It is almost always used in agile teams, being one of the core tools of agile software development. TDD was first defined and introduced to the professional community by Kent Beck in 2002. Since then, it has become an accepted – and recommended – technique in everyday programming.
TDD has three core rules:
- You are not allowed to write any production code, if there is not a failing test to warrant it.
- You are not allowed to write more of a unit test than is strictly necessary to make it fail. Not compiling / running is failing.
- You are not allowed to write more production code than is strictly necessary to make the failing test pass.