feat: Add TDD code generation workflow as optional path

[DrakeRHEE]

Add Test-Driven Development (TDD) as an opt-in extension for the Code Generation stage. When enabled, TDD replaces the standard code generation workflow with a RED-GREEN-REFACTOR cycle that prevents feature gaps and ensures high code quality.

Changes:

• Add extensions/testing/tdd/tdd-code-generation.md with full TDD workflow as extension rules
• Add extensions/testing/tdd/tdd-code-generation.opt-in.md for Requirements Analysis opt-in
• Per-unit TDD applicability check for multi-unit project flexibility
• No modifications to core-workflow.md, code-generation.md, or build-and-test.md

Design:

• Follows existing extension pattern (security-baseline, property-based-testing)
• Opt-in at Requirements Analysis phase (project level)
• Per-unit applicability check at Code Generation entry (unit level)
• Stage Applicability: Functional Design (testable property identification), Code Generation (workflow replacement), Build and Test (TDD artifact recognition)

Validation:

• Internal large-scale TTT conducted comparing TDD vs Standard paths. Teams using TDD completed development in significantly less time with more complete results (100% improvement).
• Field feedback confirmed that TDD-based AI-DLC runs produced finished outputs in a single pass or with minimal issues.
• Stability verified through multiple customer 1-day workshops with consistent, reliable results.

Co-authored-by: Jeongho Han hjeongho@amazon.com
Co-authored-by: Hyojin Jung jhyojin@amazon.com

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[DrakeRHEE]

Problem

Through three rounds of AI-DLC Unicorn Gym sessions, we observed that the Construction phase's Code Generation stage occasionally missed implementing required features. This led to incomplete deliverables and required manual intervention to identify and implement the missing functionality.

Solution

Integrated Test-Driven Development (TDD) methodology as an opt-in extension in the AI-DLC extensions framework. Users can enable TDD during Requirements Analysis, and the extension replaces the standard code generation workflow with a TDD-driven RED-GREEN-REFACTOR cycle.

Extension Design

• Opt-in: tdd-code-generation.opt-in.md — presented during Requirements Analysis (project level)
• Rules: tdd-code-generation.md — cross-cutting extension with Stage Applicability:
  • Functional Design: testable property identification
  • Code Generation: workflow replacement (TDD instead of standard)
  • Build and Test: TDD artifact recognition, skip re-running passed tests
• Per-unit flexibility: At Code Generation entry, each unit is evaluated for TDD applicability. Simple config-only units can skip TDD and fall back to standard workflow.
• No core file modifications: core-workflow.md, code-generation.md, build-and-test.md are unchanged.

TDD vs Standard Comparison

	TDD	Standard
Token cost	~1.5-2x baseline	Baseline
Feature completeness	High (test-first prevents gaps)	Occasional omissions
Wall-clock time	Faster (fewer rework cycles)	Slower (error correction overhead)
Recommended for	Complex business logic, long-term projects	Simple prototypes, one-off scripts

Test Evidence

Korea Tech TTT Session (January 30, 2026)

• Participants: ~50 Korea Tech roles
• Setup: 24 participants used TDD-enhanced steering, 14 used default steering
• Results: 100% completion rate for TDD group, completed in significantly shorter wall-clock time
• CSAT: 4.9/5.0 (38 respondents)

Partner Workshop (February 4, 2026)

• Participants: 70 engineers from 14 partner companies
• Results: 100% completion rate within one day, near-zero defect outputs
• CSAT: 4.6/5.0, 13/14 companies expressed interest in future sessions

Changes

• extensions/testing/tdd/tdd-code-generation.opt-in.md (NEW) — Opt-in prompt for Requirements Analysis
• extensions/testing/tdd/tdd-code-generation.md (NEW) — Full TDD extension rules with:
  • Stage Applicability table (Functional Design, Code Generation, Build and Test)
  • Per-unit TDD applicability check (Step 0)
  • Part 1: TDD Planning (contracts, test plan, generation plan)
  • Part 2: TDD Generation (RED-GREEN-REFACTOR cycle per method)
  • Blocking TDD finding behavior
  • Verification/compliance summary format

[harmjeff]

@DrakeRHEE Please move this to be an extensions capability.

[DrakeRHEE]

@DrakeRHEE Please move this to be an extensions capability.

@harmjeff Done :)