Pact

Pact is a contract testing tool for HTTP APIs and message-based integrations. Consumer tests record the interactions they expect from a provider as a contract, and the contract is then verified against the real provider.

The approach is intended to replace end-to-end integration environments: each service is tested in isolation against its contracts, so that services can be developed and deployed independently. Pact also covers message queues and serverless integrations.

Pact is open source and maintained by the Pact Foundation, with implementations for several languages such as pact-js, which is actively developed on GitHub.