Reliability Testing

What happens when your database is slow? When Redis is down? When a third-party API returns 500s? We inject these failures systematically and verify your application degrades gracefully: circuit breakers open, fallback responses serve, queues buffer writes, and users see a degraded but functional experience instead of a stack trace.

Incorrect timeout configuration is one of the most common causes of cascading failures. We test every inter-service timeout: HTTP clients, database connections, message queue consumers, gRPC deadlines. We verify retry policies use exponential backoff with jitter, that retry storms do not amplify failures, and that circuit breakers trip before retries exhaust the connection pool.

We verify that crashes mid-transaction do not corrupt data. Killed processes during writes should leave databases consistent. Interrupted message processing should not lose or duplicate events. We test idempotency of critical operations and verify that your system recovers to a consistent state after any single-point failure.

Reliability tests run in CI alongside your existing test suites. We use tools like Toxiproxy to inject network faults, testcontainers to spin up real dependencies, and custom harnesses to simulate partial infrastructure failures. Failed reliability tests block deployment just like failed unit tests — reliability is a first-class quality gate.