ATDD (acceptance-test-driven development)
Collaboratively writing the acceptance tests for a feature, product, dev, and QA together, before implementation begins, so 'done' becomes something executable rather than a matter of opinion. ATDD differs from TDD in scope: TDD drives unit design from the developer's view, while ATDD captures the customer-facing behaviour the whole team agreed on.
ATDD pulls the "what does done look like?" conversation to the very start, expressing acceptance criteria as executable tests before code exists. Its real value is less the automation and more the forced clarity: writing the acceptance test surfaces ambiguity in the requirement while it's still cheap to resolve. It pairs naturally with a connected backlog, where the acceptance test lives next to the story it verifies rather than in a separate tool.