Quality-Driven Development (QDD)

Quality-driven development with automatic TDD/DDD methodology selection and TRUST 5 quality framework. Use when building features, refactoring code, fixing bugs, or any coding task that needs structured quality assurance.

Quality-Driven Development

Structured development methodology inspired by MoAI-ADK's TRUST 5 framework. Automatically selects TDD or DDD based on project state, enforces quality gates, and produces tested, documented code.

Core Philosophy

"바이브 코딩의 목적은 빠른 생산성이 아니라 코드 품질이다."

Logging Strategy

All code must include meaningful logs. Logs are the first line of defense for debugging production issues.

Log Levels

Level	Purpose	Examples	운영(PRD)	개발(DEV)
ERROR	예외, 실패, 복구 불가 상황	catch 블록, DB 연결 실패, 필수값 누락	✅	✅
WARN	예상 밖 상황, 복구 가능	fallback 사용, 재시도, deprecated 호출	✅	✅
INFO	핵심 흐름만 간결하게	API 호출/응답, 상태 변경, 트랜잭션 시작/완료	✅	✅
DEBUG	상세 디버깅, 자유롭게	함수 진입/종료, 변수값, 조건 분기, 쿼리 파라미터	❌	✅

Log Placement Rules

반드시 로그를 넣어야 하는 곳:

• API 엔드포인트 진입 (INFO: 요청 파라미터 요약)
• 외부 서비스 호출 전/후 (INFO: 호출 대상, 응답 상태)
• 에러/예외 catch 블록 (ERROR: 에러 메시지 + 컨텍스트)
• 비즈니스 로직 분기점 (DEBUG: 어떤 분기로 갔는지)
• 상태 변경 (INFO: before → after)
• 배치/스케줄러 시작/완료 (INFO: 처리 건수, 소요 시간)

로그 작성 원칙:

• 운영에서 INFO만으로 흐름 추적이 가능해야 한다
• DEBUG는 부담 없이 자유롭게 — 운영에선 출력 안 됨
• 민감 정보(비밀번호, 토큰, 개인정보) 절대 로그에 포함 금지
• 로그 메시지에 컨텍스트 포함 (ID, 파라미터 등) — "처리 실패" ❌ → "주문 처리 실패 [orderId=123, reason=재고부족]" ✅

Workflow

Phase 0: Project Analysis

Before any coding, analyze the project:

1. Check if test framework exists (jest, vitest, pytest, go test, etc.)
2. Measure current test coverage (run coverage command if available)
3. Detect language, framework, and project structure
4. Identify logging framework (slf4j, winston, pino, logback, print/console.log etc.) — if none exists, recommend and set up one
5. Select methodology automatically:

text

Coverage >= 10% OR new project → TDD (default)
Coverage < 10% AND existing project → DDD

Report the analysis result and selected methodology to the user before proceeding.

Phase 1: SPEC Document

Create a SPEC document before implementation:

markdown

# SPEC-{ID}: {Title}

## Goal
One sentence describing what this change achieves.

## Acceptance Criteria
- [ ] Criterion 1 (testable)
- [ ] Criterion 2 (testable)
- [ ] Criterion 3 (testable)

## Scope
- **In scope:** What will be changed
- **Out of scope:** What will NOT be changed

## Technical Approach
Brief description of implementation strategy.

## Log Points
Key locations where logs will be added (level + message summary).

## TRUST 5 Checklist
- [ ] **Tested:** All acceptance criteria have corresponding tests
- [ ] **Readable:** Code is self-documenting with clear naming
- [ ] **Unified:** Follows existing project conventions
- [ ] **Secured:** No new vulnerabilities introduced
- [ ] **Trackable:** Changes are documented and linked to this SPEC

Phase 2A: TDD Execution (New Projects / Coverage >= 10%)

Follow RED → GREEN → REFACTOR strictly:

RED — Write failing tests first

1. Write test for first acceptance criterion
2. Run test — confirm it FAILS
3. Report: "🔴 RED: Test written and failing as expected"

GREEN — Minimal implementation

1. Write minimum code to pass the test
2. Add appropriate logs at key points (API calls, error handling, state changes)
3. Run test — confirm it PASSES
4. Report: "🟢 GREEN: Test passing"

REFACTOR — Clean up

1. Improve code quality while keeping tests green
2. Review log quality — ensure levels are correct, messages are clear with context
3. Run all tests — confirm everything still passes
4. Report: "♻️ REFACTOR: Code cleaned, all tests green"

Repeat for each acceptance criterion.

Phase 2B: DDD Execution (Existing Projects / Coverage < 10%)

Follow ANALYZE → PRESERVE → IMPROVE:

ANALYZE — Understand existing code

1. Read existing code and identify dependencies
2. Map domain boundaries and side effects
3. Check existing logging — identify gaps where logs are missing
4. Report: "🔍 ANALYZE: Current behavior documented"

PRESERVE — Capture current behavior

1. Write characterization tests for existing behavior
2. Run tests — confirm they pass against current code
3. Report: "🛡️ PRESERVE: Characterization tests in place"

IMPROVE — Change under test protection

1. Make changes incrementally
2. Add/improve logs at changed code paths
3. Run tests after each change
4. Report: "📈 IMPROVE: Changes verified by tests"

Phase 3: TRUST 5 Quality Gate

Before declaring work complete, verify all 5 principles:

Principle	Check	Action
Tested	Run full test suite	All tests pass, coverage maintained or improved
Readable	Review naming, comments, log messages	Fix unclear names, ensure log messages have context
Unified	Check style consistency, log format consistency	Match existing patterns (indent, naming, log format)
Secured	Security review, log content review	No hardcoded secrets, no sensitive data in logs
Trackable	Documentation, log coverage	Changes described, key paths have appropriate logs

Only proceed to completion when ALL 5 checks pass.

Phase 4: Completion Report

markdown

## ✅ SPEC-{ID} Complete

### Methodology: {TDD|DDD}
### Changes:
- {file1}: {what changed}
- {file2}: {what changed}

### Log Points Added:
- {file1:line}: {level} - {description}
- {file2:line}: {level} - {description}

### Test Results:
- Tests: {passed}/{total}
- Coverage: {before}% → {after}%

### TRUST 5:
- ✅ Tested | ✅ Readable | ✅ Unified | ✅ Secured | ✅ Trackable

Agent Roles

When working on complex tasks, delegate to specialized perspectives:

Role	Focus	When to Activate
Architect	System design, API contracts	New feature, structural change
Backend	API, DB, business logic	Server-side work
Frontend	UI, UX, components	Client-side work
Security	Vulnerabilities, auth, input validation	Auth features, data handling
Tester	Test strategy, edge cases, coverage	Always (TRUST 5 - Tested)
Performance	Optimization, profiling	Load-sensitive features

For each task, identify which roles are relevant and apply their perspective during review.

Reference Guides

Topic	Reference	Load When
TDD Patterns	references/tdd-patterns.md	TDD methodology selected
DDD Patterns	references/ddd-patterns.md	DDD methodology selected
TRUST 5 Detail	references/trust5-checklist.md	Quality gate phase
Language-specific	references/lang-{language}.md	Language-specific patterns needed

Constraints

MUST DO:

• Always analyze project before choosing methodology
• Always create SPEC before coding
• Always write tests (TDD: before code, DDD: before changes)
• Always run TRUST 5 gate before completion
• Report progress at each phase transition
• Always add meaningful logs with appropriate levels at key code points
• Always ensure tests are actually executed (not just written) — run the test suite and confirm results before proceeding

MUST NOT:

• Skip test writing for any reason
• Write implementation before tests (TDD mode)
• Modify untested code without characterization tests first (DDD mode)
• Declare complete without all 5 TRUST checks passing
• Change code outside the SPEC scope
• Log sensitive data (passwords, tokens, personal info)
• Skip logging at error/catch blocks