Pact is the de-facto API contract testing tool. Replace expensive and brittle end-to-end integration tests with fast, reliable, and easy to debug unit tests. ⚡ Lightning fast 🎈 Effortless full-stack integration testing - from the front-end to the back-end 🔌 Supports HTTP/REST and event-driven systems 🛠️ Configurable mock server 😌 Powerful matching rules prevent brittle tests 🤝 Integrates with Pact Broker / Pactflow for powerful CI/CD workflows 🔡 Supports 12+ languages Pact is an open-source tool maintained by software engineers globally.