api-contract-testing
Verify API contracts between services to ensure compatibility and prevent breaking changes. Use for contract testing, Pact, API contract validation, schema validation, and consumer-driven contracts.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/aj-geddes/useful-ai-prompts --skill api-contract-testing- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads api-contract-testing automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
API Contract Testing
Table of Contents
Overview
Contract testing verifies that APIs honor their contracts between consumers and providers. It ensures that service changes don't break dependent consumers without requiring full integration tests. Contract tests validate request/response formats, data types, and API behavior independently.
When to Use
- Testing microservices communication
- Preventing breaking API changes
- Validating API versioning
- Testing consumer-provider contracts
- Ensuring backward compatibility
- Validating OpenAPI/Swagger specifications
- Testing third-party API integrations
- Catching contract violations in CI
Quick Start
Minimal working example:
// tests/pact/user-service.pact.test.ts
import { PactV3, MatchersV3 } from "@pact-foundation/pact";
import { UserService } from "../../src/services/UserService";
const { like, eachLike, iso8601DateTimeWithMillis } = MatchersV3;
const provider = new PactV3({
consumer: "OrderService",
provider: "UserService",
port: 1234,
dir: "./pacts",
});
describe("User Service Contract", () => {
const userService = new UserService("http://localhost:1234");
describe("GET /users/:id", () => {
test("returns user when found", async () => {
await provider
.given("user with ID 123 exists")
.uponReceiving("a request for user 123")
.withRequest({
method: "GET",
path: "/users/123",
headers: {
// ... (see reference guides for full implementation)
Reference Guides
Detailed implementations in the references/ directory:
| Guide | Contents |
|---|---|
| Pact for Consumer-Driven Contracts | Pact for Consumer-Driven Contracts |
| OpenAPI Schema Validation | OpenAPI Schema Validation |
| JSON Schema Validation | JSON Schema Validation |
| REST Assured for Java | REST Assured for Java |
| Contract Testing with Postman | Contract Testing with Postman |
| Pact Broker Integration | Pact Broker Integration |
Best Practices
✅ DO
- Test contracts from consumer perspective
- Use matchers for flexible matching
- Validate schema structure, not specific values
- Version your contracts
- Test error responses
- Use Pact broker for contract sharing
- Run contract tests in CI
- Test backward compatibility
❌ DON'T
- Test business logic in contract tests
- Hard-code specific values in contracts
- Skip error scenarios
- Test UI in contract tests
- Ignore contract versioning
- Deploy without contract verification
- Test implementation details
- Mock contract tests
FAQ
What does the api-contract-testing skill do?
Verify API contracts between services to ensure compatibility and prevent breaking changes. Use for contract testing, Pact, API contract validation, schema validation, and consumer-driven contracts.
How do I install api-contract-testing?
Run npx skills add https://github.com/aj-geddes/useful-ai-prompts --skill api-contract-testing in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/api-contract-testing/ (personal) or .claude/skills/api-contract-testing/ (project).
Which AI agents can use api-contract-testing?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is api-contract-testing safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains api-contract-testing?
It is published by aj-geddes in aj-geddes/useful-ai-prompts. It has 914 recorded installs.
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