# Contract Testing

> Use consumer-driven or bidirectional contract tests to keep service interfaces compatible across independent deployability. Use when multiple services or teams share APIs and need confidence that changes won’t break consumers.

- Skill: `itsual/contract-testing` (Agent Skill)
- Install (CLI): `npx skillmds@latest add itsual/contract-testing`
- Raw SKILL.md: https://api.skillmd.com/api/skills/itsual/contract-testing/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: itsual (https://skillmd.com/u/itsual)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/itsual/contract-testing

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# Contract Testing

## Overview

Contract tests verify that a provider still satisfies the expectations of its consumers without requiring full end-to-end deployments for every change.

## When to Use

- Microservices or multi-team environments with shared APIs
- Independent deployment of producers and consumers
- Reducing reliance on slow, brittle E2E tests for interface compatibility

## Approaches

- Consumer-driven contracts (e.g. Pact-style)
- Provider-driven / schema-based verification
- Bidirectional contracts

## Principles

- Contracts should reflect real consumer expectations
- Keep contracts focused and maintainable
- Integrate verification into CI for both consumer and provider
- Version and evolve contracts deliberately

## Verification

- Provider CI verifies it still meets published contracts
- Consumer CI verifies it works against the contract (or a stub derived from it)
- Breaking changes are detected before production