TDD Workflow Skill

This skill guides you through the Test-Driven Development (TDD) workflow.

When to Use

• •Implementing new features
• •Refactoring existing code
• •When user requests TDD approach
• •When /tdd command is invoked

Workflow Steps

1. RED Phase - Write Failing Test

Goal: Write a test that describes the desired behavior

Steps:

1. •Identify the behavior to implement
2. •Write a test that describes this behavior
3. •Run the test - it should fail (RED)
4. •Ensure the test fails for the right reason

Example:

describe('UserService', () => {
  it('should create a new user', async () => {
    const user = await userService.create({ name: 'John' });
    expect(user.id).toBeDefined();
    expect(user.name).toBe('John');
  });
});

2. GREEN Phase - Make Test Pass

Goal: Write minimal code to make the test pass

Steps:

1. •Write the simplest code that makes the test pass
2. •Don't worry about code quality yet
3. •Run the test - it should pass (GREEN)
4. •Avoid over-engineering

Example:

async create(userData: CreateUserDto): Promise<User> {
  const user = {
    id: generateId(),
    ...userData,
    createdAt: new Date()
  };
  return user;
}

3. REFACTOR Phase - Improve Code

Goal: Improve code quality while keeping tests green

Steps:

1. •Review the code for improvements
2. •Remove duplication
3. •Improve readability
4. •Maintain test coverage
5. •Run tests to ensure they still pass

Test Coverage Requirements

• •Minimum: 80% coverage
• •Critical paths: 100% coverage
• •Edge cases: Must be tested
• •Error handling: Must be tested

Best Practices

1. •One test at a time: Focus on one behavior per test
2. •Fast feedback: Run tests frequently
3. •Clean tests: Tests should be readable
4. •Test structure: Use Arrange-Act-Assert pattern
5. •Test names: Descriptive test names that explain behavior

Common Patterns

Testing Async Code

it('should handle async operations', async () => {
  const result = await service.asyncOperation();
  expect(result).toBeDefined();
});

Testing Error Cases

it('should throw error when invalid input', async () => {
  await expect(service.operation(invalidInput))
    .rejects.toThrow('Invalid input');
});

Testing Edge Cases

it('should handle empty array', () => {
  const result = service.process([]);
  expect(result).toEqual([]);
});