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contract-testing

Testing & Quality
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Use when setting up integration testing for a frontend-backend API boundary, evaluating whether two services are safe to deploy independently, or replacing slow end-to-end tests with contract tests.

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How to use this skill

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Source SKILL.md: https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/contract-testing/SKILL.md

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Implement consumer-driven contract testing for API boundaries

Integration tests that require both services running at the same time are slow, brittle, and hard to maintain. Consumer-driven contract testing decouples the consumer and provider test suites — each team can run their tests independently, yet the broker guarantees that the published contract is always verified against the live provider. This catches API mismatches days earlier than end-to-end tests, with far less infrastructure overhead.

Quick Reference

  • The consumer writes tests that describe what it expects from the API (the "contract")
  • The contract is published to a Pact Broker and verified against the real provider
  • Provider changes that break the contract fail CI before they are deployed
  • This replaces fragile end-to-end tests that require both services to be running simultaneously

Check

Check whether the frontend has consumer-driven contract tests that define and verify the API contract with the backend.

Fix

Add Pact consumer tests for the frontend API client, publish the contracts to a broker, and add provider verification to the backend CI pipeline.

Explain

Explain how consumer-driven contract testing works, what the Pact workflow looks like end-to-end, and how it compares to mocking and end-to-end testing.

Code Review

Review the Pact consumer tests. Flag interactions that are too permissive (any-type matchers on fields the consumer actually uses), missing status code assertions, and interactions for endpoints the consumer no longer calls.

For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/en/rules/testing/contract-testing