api-testing

# API Integration Testing

Build robust test suites for your APIs.

## Testing Pyramid for APIs

```
                    ▲
                   ▲▲▲  E2E Tests
                  ▲▲▲▲▲  (Full stack, real DB, slow)
                 ▲▲▲▲▲▲▲
                ▲▲▲▲▲▲▲▲▲  Contract Tests
               ▲▲▲▲▲▲▲▲▲▲▲  (API shape validation)
              ▲▲▲▲▲▲▲▲▲▲▲▲▲
             ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲  Integration Tests
            ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲  (API + DB, services)
           ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
          ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲  Unit Tests
         ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲  (Handlers, validators, utils)
```

| Level | What It Tests | Speed | Isolation |
|-------|---------------|-------|-----------|
| **Unit** | Individual functions, validators | Fast | High |
| **Integration** | API + database, services together | Medium | Medium |
| **Contract** | API shape matches spec | Fast | High |
| **E2E** | Full request flow, real environment | Slow | Low |

## Test Types Overview

### Integration Tests

Test your API endpoints with real (or test) database.

```typescript
describe('POST /users', () => {
  it('creates a user with valid input', async () => {
    const response = await request(app)
      .post('/users')
      .send({ email: 'test@example.com', name: 'Test User' })
      .expect(201);

    expect(response.body).toMatchObject({
      id: expect.any(String),
      email: 'test@example.com',
      name: 'Test User',
    });
  });
});
```

### Contract Tests

Validate API responses match your OpenAPI spec.

```typescript
it('matches OpenAPI schema', async () => {
  const response = await request(app).get('/users/1');
  
  expect(response.body).toMatchSchema('User');
});
```

### E2E Tests

Test complete flows across multiple endpoints.

```typescript
describe('User registration flow', () => {
  it('registers, verifies email, and logs in', async () => {
    // 1. Register
    const registerRes = await request(app)
      .post('/auth/register')
      .send({ email: 'new@example.com',