testing-strategy

Guidelines for writing maintainable, reliable tests across all levels - from unit tests to integration tests. Emphasizes test structure, naming clarity, appropriate mocking, and effective test data management.

  const userData = createUserData({ email: '[email protected]' });
  passwordHasher.hash.mockResolvedValue('hashed-password');
  
  // Act
  const result = await service.createUser(userData);
  
  // Assert
  expect(result.email).toBe('[email protected]');
  expect(passwordHasher.hash).toHaveBeenCalledWith(userData.password);
  expect(mockRepository.save).toHaveBeenCalledWith(
    expect.objectContaining({ password: 'hashed-password' })
  );
});

}); });

</example>

<example type="integration-test">
```typescript
describe('User API Integration', () => {
  let app: Application;
  let database: TestDatabase;
  
  beforeAll(async () => {
    database = await TestDatabase.create();
    app = createApp(database);
  });
  
  afterAll(async () => {
    await database.cleanup();
  });
  
  describe('POST /users', () => {
    it('User_Registration_CreatesUserAndReturnsToken', async () => {
      // Arrange
      const newUser = {
        email: '[email protected]',
        password: 'SecurePass123!',
        name: 'Test User'
      };
      
      // Act
      const response = await request(app)
        .post('/users')
        .send(newUser);
      
      // Assert
      expect(response.status).toBe(201);
      expect(response.body).toMatchObject({
        user: { email: newUser.email, name: newUser.name },
        token: expect.any(String)
      });
      
      // Verify persistence
      const savedUser = await database.users.findByEmail(newUser.email);
      expect(savedUser).toBeDefined();
      expect(savedUser.password).not.toBe(newUser.password); // Should be hashed
    });
  });
});