What problem does it solve? Resilience mechanisms like bulkheads, rate limiters, and circuit breakers often ship without tests proving they actually contain failures, and database migrations risk silent data loss or irreversibility. This Skill provides concrete fault-injection test patterns and data-integrity invariants to verify both. ## Core Features & Use Cases - Resilience Pattern Testing: Pair each fault injection (dependency hang, excess traffic, repeated errors) with its expected containment behavior for bulkheads, rate limits, and circuit breakers, including full closed→open→half-open→closed state transitions. - Migration Integrity Testing: Verify four invariants—round-trip consistency (up→down→up), row-count preservation, non-NULL required columns, and aggregate consistency—against real data on a production-like database engine. - Use Case: Before deploying a migration that adds a required column, run the procedure to confirm existing rows are backfilled, row counts match, and the down migration genuinely restores the prior schema. ## Quick Start Ask the AI to apply the nonfunctional-resilience skill to write fault-injection tests for your circuit breaker and integrity checks for your latest database migration.
