SKILL.md
Testing Tdd London
Quick Start
// 1. Start with acceptance test (outside)
describe('User Registration', () => {
it('should register new user successfully', async () => {
const mockRepository = { save: jest.fn().mockResolvedValue({ id: '123' }) };
const mockNotifier = { sendWelcome: jest.fn() };
const service = new UserService(mockRepository, mockNotifier);
await service.register({ email: '[email protected]' });
// 2. Verify behavior (interactions)
expect(mockRepository.save).toHaveBeenCalledWith(
expect.objectContaining({ email: '[email protected]' })
);
expect(mockNotifier.sendWelcome).toHaveBeenCalledWith('123');
});
});When to Use
- Testing object collaborations and message passing
- Contract-driven development with clear interfaces
- Outside-in development starting from user behavior
- When isolation of units is critical
- Service orchestration testing
- Testing HOW objects work together (not WHAT they contain)
Prerequisites
- Understanding of mock objects vs stubs
- Jest, Vitest, or similar testing framework with mocking support
- Clear separation of concerns in architecture
- Dependency injection pattern in codebase
References
Version History
- 1.0.0 (2026-01-02): Initial release - converted from tdd-london-swarm agent
Sub-Skills
- [Configuration](configuration/SKILL.md)
- [Example 1: Service Orchestration Test (+2)](example-1-service-orchestration-test/SKILL.md)
- [Mock Management (+2)](mock-management/SKILL.md)
Sub-Skills
- [Execution Checklist](execution-checklist/SKILL.md)
- [Error Handling](error-handling/SKILL.md)
Sub-Skills
- [London vs Chicago School (+2)](london-vs-chicago-school/SKILL.md)
- [1. Outside-In Development (+2)](1-outside-in-development/SKILL.md)
- [Metrics & Success Criteria](metrics-success-criteria/SKILL.md)
- [MCP Tools (+2)](mcp-tools/SKILL.md)