/\
       /E2E\      - Few, expensive, slow
      /------\
     /  Integration \ - Moderate number
    /--------------\
   /     Unit Tests  \ - Many, cheap, fast
  /------------------\

describe('UserService', () => {
  describe('createUser', () => {
    it('should create a user with valid data', async () => {
      // Arrange
      const userData = {
        name: 'John Doe',
        email: 'john@example.com'
      };

      // Act
      const user = await userService.create(userData);

      // Assert
      expect(user.id).toBeDefined();
      expect(user.email).toBe(userData.email);
    });

    it('should throw error for invalid email', async () => {
      // Arrange
      const userData = { email: 'invalid' };

      // Act & Assert
      await expect(userService.create(userData))
        .rejects.toThrow('Invalid email');
    });
  });
});

describe('POST /api/users', () => {
  it('should create a user', async () => {
    const response = await request(app)
      .post('/api/users')
      .send({
        name: 'John Doe',
        email: 'john@example.com'
      })
      .expect(201)
      .expect((res) => {
        expect(res.body.id).toBeDefined();
        expect(res.body.email).toBe('john@example.com');
      });
  });
});

test('user can login', async ({ page }) => {
  await page.goto('/login');
  await page.fill('[name="email"]', 'user@example.com');
  await page.fill('[name="password"]', 'password123');
  await page.click('button[type="submit"]');

  await expect(page).toHaveURL('/dashboard');
  await expect(page.locator('h1')).toContainText('Welcome');
});

# Jest
npm test -- --coverage

# Python (pytest-cov)
pytest --cov=src --cov-report=html

# Go
go test -coverprofile=coverage.out
go tool cover -html=coverage.out

// Good: Describes what is being tested
it('should reject invalid email addresses')

// Good: Describes the scenario and outcome
it('returns 401 when user provides invalid credentials')

// Bad: Vague
it('works correctly')

python scripts/generate_test.py <filename>

python scripts/coverage_report.py