Full-Stack Architecture Patterns

Chapter 12: Testing Architecture

12.1 Testing Strategies

Comprehensive testing ensures application quality and reliability. Implement multiple testing levels for thorough coverage.

Unit Testing:

• Test individual functions/components in isolation
• Fast execution
• High coverage
• Catches bugs early

// Unit test example (Jest)
describe('UserService', () => {
    test('should create user', async () => {
        const userData = { name: 'John', email: 'john@example.com' };
        const user = await UserService.create(userData);
        
        expect(user).toHaveProperty('id');
        expect(user.name).toBe('John');
    });
    
    test('should validate email', () => {
        expect(UserService.isValidEmail('invalid')).toBe(false);
        expect(UserService.isValidEmail('test@example.com')).toBe(true);
    });
});

Integration Testing:

• Test how components work together
• Test API endpoints
• Test database interactions
• Verify system integration

// Integration test
describe('User API', () => {
    test('POST /api/users creates user', async () => {
        const response = await request(app)
            .post('/api/users')
            .send({ name: 'John', email: 'john@example.com' })
            .expect(201);
        
        expect(response.body).toHaveProperty('id');
        expect(response.body.name).toBe('John');
    });
});

End-to-End (E2E) Testing:

• Test complete user workflows
• Simulate real user interactions
• Test in browser environment
• Slower but comprehensive

// E2E test (Playwright)
test('user can register and login', async ({ page }) => {
    await page.goto('/register');
    await page.fill('#name', 'John');
    await page.fill('#email', 'john@example.com');
    await page.fill('#password', 'password123');
    await page.click('button[type="submit"]');
    
    await expect(page).toHaveURL('/dashboard');
});

12.2 Test-Driven Development

TDD (Test-Driven Development) writes tests before implementation, ensuring code meets requirements.

TDD Cycle (Red-Green-Refactor):

1. Red: Write failing test
2. Green: Write minimal code to pass test
3. Refactor: Improve code while keeping tests passing

TDD Benefits:

• Better code design
• Higher test coverage
• Documentation through tests
• Confidence in refactoring

12.3 Testing Tools

Choose appropriate testing tools for your stack.

JavaScript/Node.js:

• Jest: Popular testing framework
• Mocha: Flexible test framework
• Supertest: API testing
• Playwright/Cypress: E2E testing

PHP:

• PHPUnit: Unit testing framework
• Codeception: Full-stack testing

Python:

• pytest: Testing framework
• unittest: Built-in testing

12.4 Testing Best Practices

Follow best practices for effective testing.

• Write tests for critical functionality
• Keep tests independent and isolated
• Use descriptive test names
• Test edge cases and error conditions
• Maintain test code quality
• Run tests in CI/CD pipeline
• Aim for high coverage but focus on quality