# Tdd

> Test-Driven Development skill for the ikigai project

- Skill: `multicam/tdd` (Agent Skill)
- Install (CLI): `npx skillmds@latest add multicam/tdd`
- Raw SKILL.md: https://api.skillmd.com/api/skills/multicam/tdd/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: multicam (https://skillmd.com/u/multicam)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/multicam/tdd

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# Test-Driven Development

## Description
TDD methodology for development phase. Focus on testing what you build.

## Details

**Core principle: Write tests for the code you write.**

Follow Red/Green/Verify cycle:

### 1. Red: Write a failing test first

- Write the test code that calls the new function
- Add function declaration to header file
- Add stub implementation that compiles but does nothing (e.g., `return OK(NULL);`)
- A compilation error is NOT a failing test - you need a stub that compiles and runs
- Verify the test actually fails with assertion failures

### 2. Green: Write minimal code to make the test pass

- Implement ONLY what the test requires
- STOP immediately when the test passes
- DO NOT write "helper functions" before they're called
- DO NOT write code "because you'll need it later"

### 3. Verify: Run quality checks

- `check-unit --file=PATH` - Test must pass
- `check-filesize --file=PATH` - File size under 16KB
- `check-complexity --file=PATH` - Function complexity under threshold

## Development Phase Focus

**Test what you build.** During development:

- Write tests for the happy path
- Write tests for obvious error cases
- Cover the main functionality thoroughly
- Keep momentum - don't get stuck on edge cases

**Coverage gaps are OK during development.** They will be closed in a dedicated coverage phase before release.

**The test should come first** - but don't let perfect coverage slow down feature development.

If writing a helper function, ask: "Does a passing test call this right now?" If no, DELETE IT.

## Coverage Phase (Strict Mode)

**ABSOLUTE RULE: NEVER WRITE CODE BEFORE YOU HAVE A TEST THAT NEEDS IT.**

When closing coverage gaps, the verify step adds:

- `check-coverage` — **90% coverage is MANDATORY**

**Hunt every branch:**

- Test all error paths (use mocks to trigger failures)
- Test assertion violations (`tcase_add_test_raise_signal` with SIGABRT)
- Test edge cases (empty, null, boundary conditions)
- Only use `LCOV_EXCL` markers when genuinely untestable (OOM, impossible states)

If a branch is uncovered, ask: "Can I write a test for this?" If yes, WRITE IT.