ATDD
ATDD (Acceptance Test-Driven Development) is a development methodology in which the entire team defines acceptance test criteria before development begins, automates those tests, and then proceeds with implementation.
## Differences from TDD While TDD drives a developer's code design, ATDD aims to align the entire team's understanding of business requirements. Just as TDD follows a "RED → GREEN → Refactor" cycle, ATDD has its own distinct cycle: 1. **Discuss**: The product owner, developers, and QA discuss requirements and agree on acceptance criteria through concrete examples. 2. **Distill**: The agreed-upon criteria are translated into a structured format such as Given-When-Then. 3. **Develop**: Acceptance tests are automated, and implementation begins with the tests in a RED state. 4. **Demo**: Once the tests turn GREEN, the results are demonstrated to stakeholders. ## Three Amigos At the heart of ATDD is the "Three Amigos" session held before implementation. By discussing acceptance criteria from three perspectives — business, development, and testing — ambiguities and misalignments in the specification are resolved early. This is highly effective in preventing rework caused by misunderstandings that only surface after coding has begun. ## Barriers to Adoption Because ATDD affects the entire development process, it cannot be started simply by introducing a tool. The whole team needs to become comfortable with writing acceptance criteria, and active involvement from the product owner is essential. A practical approach is to start with a single user story, experience the benefits firsthand, and then gradually expand the scope.
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