Learn in the textbookAgile Development and XP Practices
DefinitionTest-driven development (テスト駆動開発) is a way of working in which you first write the test for a feature, then write the code that passes it.
ExplanationThe test written first states what counts as done, so the specification is clear before any code exists. The small loop of writing a test, passing it and tidying up repeats many times, with the tests checking the behavior each round. Its abbreviation is TDD, and it is one of the signature practices of XP.
AnalogyIt is like deciding, before putting a shelf together, that it must hold 30 books without tilting, and only then starting to build.
Memory hook"Driven" means pushed forward by something. Here the test leads the way and pulls the development along.