Contract Testing for Microservices#

Integration tests verify that services work together, but they require all services to be running. In a system with 20 services, running full integration tests is slow, brittle, and blocks deployments. Contract testing solves this by verifying service interactions independently – each service tests against a contract instead of against a live instance of every dependency.

The Problem with Integration and E2E Tests#

A traditional integration test for “order service calls payment service” requires both services running, along with their databases, message brokers, and any other dependencies. Problems: