Martin Fowler

Test-Driven Development (TDD) is a technique for building software that guides software development by writing tests. It was developed by Kent Beck in the late 1990’s as part of Extreme Programming. In essence we follow three simple steps repeatedly:

Write a test for the next bit of functionality you want to add. Write the functional code until the test passes. Refactor both new and old code to make it well structured.

Although these three steps, often summarized as Red – Green – Refactor, are the heart of the process, there’s also a vital initial step where we write out a list of test cases first. We then pick one of these tests, apply red-green-refactor to it, and once we’re done pick the next. Sequencing the tests properly is a skill, we want to pick tests that drive us quickly to the salient points in the design.

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