sdd-mcp: Skill for Claude Code

SDD Test Generation

Generate comprehensive tests following Test-Driven Development (TDD) methodology. Write tests that serve as living documentation and ensure code correctness.

TDD Philosophy

"Write a failing test before you write the code to make it pass."

Tests are not an afterthought—they're a design tool that:

1. Document behavior - Tests show how code is intended to be used
2. Prevent regressions - Catch bugs before they ship
3. Enable refactoring - Change with confidence
4. Drive design - Writing tests first leads to better interfaces

The TDD Cycle

┌─────────────────────────────────────┐
│                                     │
│   ┌─────────┐   Write failing test  │
│   │   RED   │◄──────────────────────┤
│   └────┬────┘                       │
│        │                            │
│        ▼ Make it pass               │
│   ┌─────────┐                       │
│   │  GREEN  │                       │
│   └────┬────┘                       │
│        │                            │
│        ▼ Improve code               │
│   ┌─────────┐                       │
│   │REFACTOR │───────────────────────┘
│   └─────────┘
└─────────────────────────────────────┘

Workflow

Step 1: Identify Test Scope

/sdd-test-gen src/services/UserService.ts           # Generate tests for file
/sdd-test-gen UserService.createUser                # Generate for specific method
/sdd-test-gen src/services/ --integration           # Integration tests for module

Step 2: Analyze the Code

Before generating tests:

1. Read the source file to understand its behavior
2. Check existing tests (if any) to avoid duplication
3. Review related requirements in .spec/specs/
4. Identify dependencies that need mocking

Step 3: Test File Structure

Generate tests with this structure:

import { UserService } from '../UserService';
import { UserRepository } from '../../repositories/UserRepository';
import { EmailService } from '../../services/EmailService';

// Mock dependencies
jest.mock('../../repositories/UserRepository');
jest.mock('../../services/EmailService');

describe('UserService', () => {
  let userService: UserService;
  let mockUserRepo: jest.Mocked<UserRepository>;
  let mockEmailService: jest.Mocked<EmailService>;

  beforeEach(() => {
    jest.clearAllMocks();
    mockUserRepo = new UserRepository() as jest.Mocked<UserRepository>;
    mockEmailService = new EmailService() as jest.Mocked<EmailService>;
    userService = new UserService(mockUserRepo, mockEmailService);
  });

  describe('createUser', () => {
    it('should create a user with valid input', async () => {
      // Arrange
      const input = { email: '[email protected]', name: 'Test User' };
      mockUserRepo.save.mockResolvedValue({ id: '1', ...input });

      // Act
      const result = await userService.createUser(input);

      // Assert
      expect(result.id).toBeDefined();
      expect(mockUserRepo.save).toHaveBeenCalledWith(expect.objectContaining(input));
    });

    it('should throw error when email already exists', async () => {
      // Arrange
      mockUserRepo.findByEmail.mockResolvedValue({ id: '1', email: '[email protected]' });

      // Act & Assert
      await expect(userService.createUser({ email: '[email protected]' }))
        .rejects.toThrow('Email already exists');
    });
  });
});