tdd-workflow

Test-Driven Development requires writing failing tests first, then implementing code to pass them. Start by defining what your feature should do—write assertions for business logic, error cases (like 401 or 400 responses), and edge cases—commit those tests before writing implementation code. This ensures tests remain immutable guardrails against bugs.

AI agents can produce plausible but incorrect code. TDD prevents this by enforcing immutable tests before implementation, making tests reliable checkpoints. Red-Green-Refactor cycles ensure your AI assistant builds to spec without modifying tests to hide failures, catching hallucinations early.

Enforce five must-pass criteria: tests verify business logic, cover error paths and edge cases, use meaningful assertions, focus on observable behavior, and maintain minimum coverage thresholds (≥80% statements, ≥75% branches). Vitest integration automates coverage verification and detects when tests don't genuinely validate behavior.

The two-phase TDD approach commits tests in the RED phase before any implementation begins. Lock tests in version control, then move to GREEN (implement) and REFACTOR phases without touching test files. This workflow structure prevents accidental or intentional test modifications that mask implementation failures.

Yes. Vitest runs automated test quality and coverage checks, enforcing minimum thresholds and detecting cheating patterns like overly broad assertions or missing edge cases. Integration with your TypeScript/Wasp project provides immediate feedback on whether tests meet reliability standards.