Test-driven development is a collection of practices typified by writing new production code by first writing a failing test that demands the code into existence. Its proponents point to values that range from reducing defects to improving code design. Oft-cited ancillary benefits point to improved productivity via increased focus, tighter feedback loops, and lessening the impulse to future-proof solutions.

The TDD label has been used in dozens of contexts and claimed by hundreds of practitioners, so there are a number of varying opinions as to what TDD is and isn't. This wiki discusses a few of them (in, admittedly, very broad strokes):

• "Classical" or Detroit-school TDD
• "Mockist" or London-school TDD
• [Discovery Testing]], an iteration on ideas from [London-school

See also:

• Wikipedia