What is a comprehensive testing strategy for microservices?

Testing microservices requires a layered strategy because different test types provide different trade-offs between confidence and speed. Unit tests (the base of the pyramid) test individual business logic functions in isolation — fast, cheap, run on every commit. Integration tests verify that a service correctly integrates with its own database, cache, and message broker (using Testcontainers to spin up real Docker dependencies) — slower but catch infrastructure wiring bugs. Consumer-driven contract tests (Pact) verify service-to-service API compatibility without live dependencies — fast and precise. Component tests test the full service in isolation with all external dependencies mocked — validate the full service behavior. End-to-end tests (the peak of the pyramid) run against a full deployed environment — provide the highest confidence but are slowest, flakiest, and most expensive. The goal is to maximize contract and component test coverage while minimizing the expensive end-to-end suite, catching most integration bugs without requiring a full environment deployment for every commit.