Consumer-Driven Contract Testing
Consumer-driven contract testing has API consumers define the exact requests and responses they expect from a provider, generating a "contract" that's then independently verified against the real provider — catching breaking changes in the provider's own pipeline, before they ever reach a consumer in production.
The workflow: a consumer team writes tests against a mock of the provider based on what they need, which generates a contract file (Pact is the most common tool for this). That contract is published and then replayed against the real provider's own test suite — if the provider's actual behavior doesn't match, the provider's build fails, not the consumer's.
This flips the traditional integration-testing relationship: instead of the provider guessing what consumers need or consumers discovering breakage after a bad deploy, the provider gets direct, automated feedback about exactly what would break, for exactly which consumers, before anything ships.
