Acceptance Test-Driven Development
Also known as: ATDD
Acceptance Test-Driven Development (ATDD) is a collaborative practice where the team — developer, tester, and business stakeholder — agrees on concrete acceptance tests for a feature before any code is written, then builds to make those tests pass. It turns acceptance criteria into an executable definition of done.
ATDD sits close to BDD, and the two are often conflated, but ATDD emphasizes the three-way conversation (business, dev, test) that produces the acceptance criteria, while BDD emphasizes the Given/When/Then language those criteria get written in. Many teams practice both together without drawing a hard line.
The practical payoff is the same one TDD offers at a smaller scale: writing the test first forces the acceptance criteria to be concrete and unambiguous before implementation starts, catching vague or contradictory requirements while they're still cheap to fix.
