# Contract Testing

> Contract Testing is an Agent Skill for testing & quality published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

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.

- Skill name: `contract-testing`
- Category: [Testing & Quality](https://www.openparable.com/skill/testing-quality/1)
- Source: https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/contract-testing/SKILL.md
- Repository: thedaviddias/Front-End-Checklist (73,218 GitHub stars when collected)

## SKILL.md

# 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.

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

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

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Source: https://www.openparable.com/skill/testing-quality/contract-testing (OpenParable). Cite the canonical URL above.