contract-testing

Contract testing automatically verifies that API changes remain backward compatible by comparing consumer expectations against provider implementations. CI/CD integration blocks deployments when breaking changes are detected, preventing service disruptions across microservices and distributed teams.

Pact defines consumer-driven contracts capturing actual interaction expectations, while OpenAPI schema validation checks structural compliance against formal specifications. Both detect incompatibilities; Pact emphasizes consumer needs, OpenAPI ensures schema conformance.

Contract testing applies to microservices architectures and third-party API integrations by enforcing agreements between consumers and providers. It verifies provider compliance against consumer contracts and detects breaking changes regardless of service boundaries or deployment scope.

Contract testing guides versioning decisions by identifying which API changes are backward compatible or require major version bumps. It enforces semantic versioning discipline by reporting violations and preventing deployments that break established contracts.

Contract testing supports multiple definition formats including Pact patterns, OpenAPI/Swagger schemas, and JSON Schema checks. You can define consumer expectations without deep schema expertise; the framework handles validation across formats.

Provider verification reports contract violations, detailing which consumer expectations the provider fails to meet. CI/CD integration prevents deployment of non-compliant providers, ensuring contracts remain enforceable before changes reach production.