# Tdd

> Test-driven development workflow for a module feature Use when this capability is needed.

- Skill: `tomevault-io/tdd-28` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/tdd-28`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/tdd-28/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Productivity
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/tdd-28

---


Implement a feature using Test-Driven Development (RED-GREEN-REFACTOR).

**Module:** $ARGUMENTS

## TDD Workflow

### Phase 1: RED — Write Failing Tests

1. Create test file at `packages/server/src/modules/<module>/__tests__/<feature>.test.ts`
2. Write test cases that describe the expected behavior:
   - Happy path
   - Edge cases
   - Error cases (domain errors)
3. Run `bun test <test-file>` — confirm tests FAIL (this is expected)

### Phase 2: GREEN — Implement Minimum Code

1. Write the minimum code to make all tests pass
2. Follow project conventions:
   - Domain entities: pure TypeScript, no Effect
   - Use cases: `Effect.gen(function* () { ... })`
   - Ports: `Context.Tag` interfaces
   - Adapters: `Layer.effect` implementations
3. Run `bun test <test-file>` — confirm all tests PASS

### Phase 3: REFACTOR — Clean Up

1. Remove duplication
2. Improve naming
3. Ensure Clean Architecture compliance
4. Run `bun test <test-file>` — confirm tests still PASS
5. Run `bun tsc --noEmit` — confirm no type errors

## Testing Conventions

- Use `bun:test` (`describe`, `it`, `expect`)
- Test domain logic as pure functions (no Effect needed)
- Test use cases with mock Layers: `Layer.succeed(MyPort, { ... })`
- Describe behavior, not implementation: "creates a character with valid stats"
- See `.claude/rules/testing.md` for full conventions

## Output

After completing all phases, report:
- Tests written (count)
- Tests passing (count)
- Files created/modified (list)

---
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<!-- tomevault:4.0:skill_md:2026-04-16 -->