Belajar Quality Engineer - Contract Testing

#Pendahuluan

Setelah di episode 3 kita mempelajari test automation mastery, pada episode ini kita mempelajari contract testing — bagaimana menguji kontrak antara service menggunakan consumer-driven contracts. Dalam arsitektur microservices, contract testing memastikan service bisa berkomunikasi tanpa integration testing yang berat.

Mengapa contract testing penting? Karena dalam microservices, banyak service yang berinteraksi. Tanpa contract testing, perubahan di satu service bisa merusak service lain tanpa terdeteksi. Contract testing memberikan fast feedback tanpa harus menjalankan semua service.

#Consumer-Driven Contracts

#Konsep Contract

text

Contract Testing:
├── Consumer: Service yang menggunakan API
├── Provider: Service yang menyediakan API
├── Contract: Agreement tentang API shape
└── Verification: Provider memverifikasi contract

#Pact Framework

text

Pact Workflow:
├── 1. Consumer writes contract
│   └── Define expected interactions
├── 2. Consumer test runs
│   └── Pact generates contract file
├── 3. Contract shared ke Provider
│   └── Via Pact Broker or file
├── 4. Provider verifies contract
│   └── Run pact-verification
└── 5. Results shared
    ├── Pass: Compatible
    └── Fail: Breaking change detected

#Practical: Pact Setup

#Consumer Test

typescript

// consumer.spec.ts
import { Pact } from '@pact-foundation/pact';
 
const provider = new Pact({
  consumer: 'OrderService',
  provider: 'UserService',
  port: 1234,
});
 
describe('User API Contract', () => {
  beforeAll(() => provider.setup());
  afterAll(() => provider.finalize());
 
  it('should return user by id', async () => {
    // Arrange
    await provider.addInteraction({
      state: 'user exists',
      uponReceiving: 'a request for user 1',
      withRequest: {
        method: 'GET',
        path: '/users/1',
      },
      willRespondWith: {
        status: 200,
        body: {
          id: 1,
          name: 'John Doe',
          email: 'john@test.com',
        },
      },
    });
 
    // Act
    const response = await fetch('http://localhost:1234/users/1');
    const user = await response.json();
 
    // Assert
    expect(user.name).toBe('John Doe');
  });
});

#Provider Verification

typescript

// provider.spec.ts
import { Verifier } from '@pact-foundation/pact';
 
describe('User API Verification', () => {
  it('validates the expectations of OrderService', async () => {
    await new Verifier({
      providerBaseUrl: 'http://localhost:3000',
      pactUrls: ['./pacts/OrderService-UserService.json'],
    }).verifyProvider();
  });
});

Note

Contract testing bukan pengganti integration testing. Ia lebih cepat dan lebih focused pada API compatibility. Gunakan contract testing untuk testing kontrak, dan integration testing untuk testing behavior.

#Contract Testing vs Integration Testing

Aspek	Contract Testing	Integration Testing
Speed	Sangat cepat	Sedang
Scope	API contract	Full integration
Dependencies	Mock provider	Real provider
Feedback	Fast	Slow
Cost	Murah	Mahal

#Practical: Contract Management

yaml

contract_management:
  consumer:
    - write_contract
    - run_consumer_test
    - publish_to_broker
  provider:
    - fetch_contracts
    - run_verification
    - publish_results
  broker:
    - store_contracts
    - track_compatibility
    - alert_on_breaking

Tip

Mulai dengan contract testing untuk service critical saja. Jangan coba implement contract testing untuk semua service sekaligus. Bertahap lebih baik daripada big bang.

#Penutup

Pada episode 4 ini, kalian telah mempelajari contract testing.

Inti yang harus dibawa pulang:

Contract testing memastikan kompatibilitas antara consumer dan provider.
Pact adalah framework populer untuk consumer-driven contracts.
Contract testing lebih cepat dari integration testing.
Pact Broker memudahkan contract management.

Di episode 5 selanjutnya, kita akan membahas API & microservices quality — bagaimana menguji API dan microservices secara komprehensif. Sampai jumpa di episode 5!