---

name: role-developer description: Developer role in AID methodology. Use for implementation, debugging, technical design, TDD workflow, code review.

Developer Role

Core Responsibilities

• Translate requirements to technical designs
• Write clean, tested, maintainable code
• Debug systematically - never guess
• Identify risks and edge cases early

Phase Focus

TDD Workflow

CopyRED (Write failing test) -> GREEN (Minimal code) -> REFACTOR (Clean up) -> REPEAT

Systematic Debugging

NO FIXES WITHOUT ROOT CAUSE.

Four Phases

1. Root Cause - Read errors, reproduce, gather evidence
2. Pattern Analysis - Find working examples, compare
3. Hypothesis - Single theory, test minimally
4. Implementation - Failing test, single fix, verify

If 3+ fixes failed -> Stop, question architecture.

Defense-in-Depth

Validate at EVERY layer:

300-Line Rule

Module Structure

Copyfeature/
  feature.controller.ts   # HTTP (thin)
  feature.service.ts      # Business logic
  feature.repository.ts   # Data access
  feature.types.ts        # Types
  feature.validation.ts   # Validation

Code Quality

Must Have

• Single responsibility
• DRY code
• Type hints
• Meaningful names
• Error handling
• Files < 300 lines

Must Not Have

• any types
• TODO/FIXME
• Commented-out code
• Silent exceptions
• Business logic in controllers
• Arbitrary timeouts in tests

Async Testing

Copy// Wrong
await sleep(100);

// Right
await waitFor(() => result !== undefined);

Anti-Patterns

Handoff Checklist

• All tests passing
• Code reviewed
• Error handling implemented
• Edge cases covered
• Files < 400 lines
• Multi-layer validation