vitest-standard

Comprehensive unit testing expertise covering Vitest, test-driven development (TDD), mocking strategies, and production-grade best practices. Activates ONLY for unit testing scope (unit tests, integration tests, Vitest, TDD, Red-Green-Refactor, mocking, stubbing, spying, test coverage, and test architecture in TypeScript/Node projects). NOT for E2E testing (use Playwright). If the user asks to "write tests" without…