MODE_Backend_TDD

Test-driven development for NestJS involves writing failing unit tests first, then implementing minimal code to pass them using the Red-Green-Refactor cycle. This Skill automates that workflow, enforcing interface-driven design, dependency injection, and Clean Architecture patterns to achieve ≥80% test coverage while maintaining code quality gates.

Clean Architecture separates your backend into distinct domain, application, and infrastructure layers. This layered approach enables testable contracts and interface-driven design, making it easier to isolate and test business logic independently of frameworks and external dependencies.

Yes. TDD with NestJS dependency injection works through contract-first modeling—define service interfaces before implementations, then inject dependencies. This Skill applies DI-based wiring and interface-driven design to ensure your tests drive architecture decisions and maintain strict testability.

This Skill automates metrics reporting including test coverage percentage, complexity scores, and execution time. It enforces coverage ≥80% and complexity <10% as quality gates, surfacing metrics so you can refactor critical services and maintain standards throughout development.

TDD is essential for MVP development under mandatory quality standards, refactoring critical services, or projects requiring high test coverage and architecture alignment. Use it when design quality, maintainability, and risk mitigation justify the upfront investment in tests-first cycles.