Testing
HTTP contract testing is well understood. You define the request and response, Pact records them as a contract, and the provider verifies it. But microservices don't only communicate over HTTP — they publish and consume events through Kafka topics, SQS queues, and SNS topics. Those async channels need contracts
Testing
Testing message ordering and exactly-once delivery in event-driven systems is one of the hardest testing problems in distributed systems engineering. The guarantees are subtle, the failure modes are nondeterministic, and most bugs only surface under specific timing or load conditions. This guide covers how to write deterministic tests
Testing
Testing asynchronous, event-driven systems is genuinely hard. The problems stack up fast: you can't assert response.status_code == 200 when the operation happens asynchronously; your test needs to know when to stop waiting; race conditions create flaky tests that pass locally and fail in CI; and the
Testing
Kafka Streams provides a TopologyTestDriver that runs your entire stream processing topology in-process — no Kafka cluster needed. You pipe records in through TestInputTopic, read results from TestOutputTopic, and advance wall-clock time programmatically to test windowed aggregations. For Schema Registry integration, use MockSchemaRegistryClient to avoid hitting a real registry.
Testing
RabbitMQ, NATS, and Kafka have dramatically different testing developer experiences. NATS wins on speed and simplicity with its embedded server. RabbitMQ is straightforward with Testcontainers. Kafka requires the most setup but has the richest ecosystem for testing. This comparison helps you understand what you're signing up for before
Testing
Event-driven architectures are notoriously difficult to test. The fundamental challenge: your service publishes an event and returns immediately. The effect of that event — a record updated in another service, a notification sent, an inventory count decremented — happens asynchronously, possibly seconds later, possibly on a different server. Traditional request/response