api-contract-testing
Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact. Use when testing microservices communication, preventing breaking changes, or validating OpenAPI specifications.
- Installs
- 480
- Last 24h
- —
- Trending rank
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- Security
- Not audited
Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/secondsky/claude-skills --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
Verify that APIs honor their contracts between consumers and providers without requiring full integration tests.
Key Concepts
| Term | Definition |
|---|---|
| Consumer | Service that calls an API |
| Provider | Service that exposes an API |
| Contract | Agreed request/response format |
| Pact | Consumer-driven contract testing tool |
| Schema | Structure definition (OpenAPI, JSON Schema) |
| Broker | Central repository for contracts |
Pact Consumer Test (TypeScript)
import { PactV3, MatchersV3 } from '@pact-foundation/pact';
const provider = new PactV3({
consumer: 'OrderService',
provider: 'UserService'
});
describe('User API Contract', () => {
it('returns user by ID', async () => {
await provider
.given('user 123 exists')
.uponReceiving('a request for user 123')
.withRequest({ method: 'GET', path: '/users/123' })
.willRespondWith({
status: 200,
body: MatchersV3.like({
id: '123',
name: MatchersV3.string('John'),
email: MatchersV3.email('john@example.com')
})
})
.executeTest(async (mockServer) => {
const response = await fetch(`${mockServer.url}/users/123`);
expect(response.status).toBe(200);
});
});
it('returns 404 for non-existent user', async () => {
await provider
.given('user does not exist')
.uponReceiving('a request for non-existent user')
.withRequest({ method: 'GET', path: '/users/999' })
.willRespondWith({
status: 404,
body: MatchersV3.like({
error: { code: 'NOT_FOUND', message: MatchersV3.string() }
})
})
.executeTest(async (mockServer) => {
const response = await fetch(`${mockServer.url}/users/999`);
expect(response.status).toBe(404);
});
});
});
Provider Verification
import { Verifier } from '@pact-foundation/pact';
new Verifier({
provider: 'UserService',
providerBaseUrl: 'http://localhost:3000',
pactBrokerUrl: process.env.PACT_BROKER_URL,
publishVerificationResult: true,
providerVersion: process.env.GIT_SHA,
stateHandlers: {
'user 123 exists': async () => {
await db.users.create({ id: '123', name: 'John' });
},
'user does not exist': async () => {
await db.users.deleteAll();
}
}
}).verifyProvider();
OpenAPI Validation (Express)
const OpenApiValidator = require('express-openapi-validator');
app.use(OpenApiValidator.middleware({
apiSpec: './openapi.yaml',
validateRequests: true,
validateResponses: true,
validateSecurity: true
}));
Additional Implementations
- Python JSON Schema: See references/python-json-schema.md
- Java REST Assured: See references/java-rest-assured.md
- Pact Broker CI/CD: See references/pact-broker-cicd.md
Best Practices
Do:
- Test from consumer perspective
- Use matchers for flexible matching
- Validate structure, not specific values
- Version contracts explicitly
- Test error responses
- Run tests in CI pipeline
- Test backward compatibility
Don't:
- Test business logic in contracts
- Hard-code specific values
- Skip error scenarios
- Ignore versioning
- Deploy without verification
Tools
- Pact - Multi-language consumer-driven contracts
- Spring Cloud Contract - JVM ecosystem
- OpenAPI/Swagger - Schema-first validation
- Dredd - API blueprint testing
- Spectral - OpenAPI linting
FAQ
What does the api-contract-testing skill do?
Verifies API contracts between services using consumer-driven contracts, schema validation, and tools like Pact. Use when testing microservices communication, preventing breaking changes, or validating OpenAPI specifications.
How do I install api-contract-testing?
Run npx skills add https://github.com/secondsky/claude-skills --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 secondsky in secondsky/claude-skills. It has 480 recorded installs.
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