contract-testing

Contract Testing

When to use

• Building microservices that need integration confidence
• Replacing brittle integration tests with faster contract tests
• Detecting breaking API changes before deployment
• Setting up provider verification in CI

Core principles

1. Consumer drives the contract — the client defines what it actually needs
2. Provider verifies against consumer contracts — not against a human-written spec
3. Contracts live in Pact Broker — visible to all teams, tracked over time
4. State handlers make tests reproducible — provider sets up data for each interaction
5. Can-I-Deploy check — never deploy a provider that breaks a consumer contract

References available

• references/consumer-pact-test.md — PactV3 setup, MatchersV3, interaction definition, executeTest
• references/provider-verification.md — Verifier config, stateHandlers, Pact Broker publish, CI flags
• references/openapi-validation.md — express-openapi-validator middleware, validateResponses in staging
• references/can-i-deploy.md — pact-broker CLI check, CI gate before deploy, exit code semantics