Contract Test Writer

Write consumer-driven contract tests (Pact)

Write consumer-driven contract tests using Pact.

Instructions

1. Install Pact:

npm install -D @pact-foundation/pact

2. Consumer test (frontend/calling service):

import { PactV3 } from '@pact-foundation/pact';

const provider = new PactV3({
  consumer: 'FrontendApp',
  provider: 'UserService',
});

describe('User API Contract', () => {
  it('should return user by id', async () => {
    provider
      .given('user 1 exists')
      .uponReceiving('a request for user 1')
      .withRequest({ method: 'GET', path: '/api/users/1' })
      .willRespondWith({
        status: 200,
        body: {
          id: 1,
          name: MatchersV3.string('Alice'),
          email: MatchersV3.email(),
        },
      });

    await provider.executeTest(async (mockServer) => {
      const client = new UserClient(mockServer.url);
      const user = await client.getUser(1);
      expect(user.name).toBeDefined();
    });
  });
});

3. Publish pact to broker, then verify on provider side.

When to Use

• Microservices architecture where teams own different services
• Frontend consuming backend APIs
• Any service-to-service communication