Build saga transaction tests - orchestration vs choreography variants, per-step compensating-action verification, partial-failure scenarios (Step 3 fails → Steps 1+2 must compensate), idempotency of compensations, outbox pattern for atomic DB-update + message-publish. Per microservices.io/saga; tests guard against ACD-without-Isolation anomalies. Use when a business transaction spans two or more services and the compensating paths for a mid-sequence failure have no coverage, or right after compensation logic changes.