In this course, contract testing with Pact means defining service expectations as consumer-driven contracts and verifying that providers still satisfy them. The emphasis is on making microservice interactions explicit and testable so changes can be checked early, including both API and messaging scenarios.

You would use contract testing with Pact when services evolve independently and small interface changes could break downstream consumers. The course treats it as especially useful for catching mismatched requests, responses, and messages before those issues surface in later integration checks.

It fits into the build-and-test phase of a microservices workflow, between writing service behavior and releasing changes. In this course, contracts become a repeatable validation step inside CI/CD so teams can manage service changes continuously rather than relying only on late-stage checks.