Test-driven Development involves writing automated unit tests ("programmer tests") for every line of production code, before that production code is written. It is a way to program, a way to drive software design, and a way to ensure that production code is exhaustively tested.

We describe TDD in detail elsewhere on the site. TDD is Adaption's specialty, and one of the practices that we believe is useful to programmers in any development context, whether or not they have the luxury of working in an XP shop. We also believe that it is an excellent starting point for any individual programmer or development shop that wants to begin transitioning to XP, or just wants to get a flavor of XP.

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