charon-fan/test-automator

Test Automator

Expert in creating and maintaining automated tests for various frameworks and languages.

When This Skill Activates

Activates when you:

• Ask to write tests
• Mention test automation
• Request test coverage improvement
• Need to set up testing framework

Testing Pyramid

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

Unit Testing

Principles

1. Test behavior, not implementation
2. One assertion per test (generally)
3. Arrange-Act-Assert pattern
4. Descriptive test names

Example (Jest)

describe('UserService', () => {
  describe('createUser', () => {
    it('should create a user with valid data', async () => {
      // Arrange
      const userData = {
        name: 'John Doe',
        email: '[email protected]'
      };

      // 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');
    });
  });
});

Integration Testing

Principles

1. Test component interactions
2. Use test doubles for external services
3. Clean up test data
4. Run in isolation

Example (Supertest)

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

E2E Testing

Principles

1. Test critical user flows
2. Use realistic test data
3. Handle async operations properly
4. Clean up after tests

Example (Playwright)

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

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

Test Coverage

Coverage Goals

| Type | Target | |------|--------| | Lines | > 80% | | Branches | > 75% | | Functions | > 80% | | Statements | > 80% |

Coverage Reports

# 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

Testing Best Practices

DO's

• Write tests before fixing bugs (TDD)
• Test edge cases
• Keep tests independent
• Use descriptive test names
• Mock external dependencies
• Clean up test data

DON'Ts

• Don't test implementation details
• Don't write brittle tests
• Don't skip tests without a reason
• Don't commit commented-out tests
• Don't test third-party libraries

Test Naming Conventions

// 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')

Common Testing Frameworks

| Language | Framework | Command | |----------|-----------|---------| | TypeScript/JS | Jest, Vitest | npm test | | Python | pytest | pytest | | Go | testing | go test | | Java | JUnit | mvn test | | Rust | built-in | cargo test |

Scripts

Generate test boilerplate:

python scripts/generate_test.py <filename>

Check test coverage:

python scripts/coverage_report.py

References

• references/best-practices.md - Testing best practices
• references/examples/ - Framework-specific examples
• references/mocking.md - Mocking guidelines