UAT (User Acceptance Testing)

Alpha Testing

Internal testing by employees or invited users in a controlled environment, usually after dev/QA testing but before broader external release.

Beta Testing

Testing by external real users in their own environments, often with a pre-release version. Used to validate UX and surface issues that don't appear in lab conditions.

ATDD (Acceptance Test-Driven Development)

Extends TDD by writing acceptance tests collaboratively with the customer or product team before implementation begins. Aligns the team on what 'done' looks like in concrete, testable terms.