# Nw Tdd Methodology > Deep knowledge for Outside-In TDD - double-loop architecture, ATDD integration, port-to-port testing, walking skeletons, and test doubles policy - Skill: `nwave-ai/nw-tdd-methodology-3` (Agent Skill) - Install (CLI): `npx skillmds@latest add nwave-ai/nw-tdd-methodology-3` - Raw SKILL.md: https://api.skillmd.com/api/skills/nwave-ai/nw-tdd-methodology-3/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Integrations & APIs - Author: nWave-ai (https://skillmd.com/u/nwave-ai) - Updated: 2026-09-21 - Page: https://skillmd.com/skills/nwave-ai/nw-tdd-methodology-3 --- # Outside-In TDD Methodology Lean composing core. The deep knowledge is decomposed into seven one-job-one-trigger modules under the `nw-tdd-methodology-*` prefix. This core keeps the name (shared — the crafters, acceptance-designer, distill, and the test-optimizer all reference it) and routes to the module whose trigger fires. Load the module(s) for the job in play; do not re-inline their content here. ## Composition — module → trigger | Module | Job | Trigger (when to load) | |--------|-----|------------------------| | `nw-tdd-methodology-cycle` | the DELIVER cycle | running RED→GREEN→COMMIT — phase boundaries, fail-for-right-reason gate, GREEN-matches-public-contract, no-code-without-a-requiring-test, post-GREEN wiring check, language-detection frame | | `nw-tdd-methodology-outside-in` | workflow shape | deciding the development-workflow shape — double-loop, Outside-In vs Inside-Out, lightweight ATDD, BDD, Bache workflow, unit-of-behavior framing | | `nw-tdd-methodology-port-to-port` | test boundary | deciding what a test enters/asserts on — port-to-port discipline, the layer-specific Universe, refactoring-resilience, hexagonal per-layer strategy | | `nw-tdd-methodology-test-doubles` | choose a double | choosing/building a test double — Meszaros taxonomy, classical-vs-mockist, mock-only-at-port-boundaries policy, doubles-must-validate-inputs contract | | `nw-tdd-methodology-walking-skeleton` | build a WS | building/validating a walking skeleton — WS protocol, per-slice JIT E2E, Mandate 5 adapter-strategy decision tree, Mandate 6 adapter real-I/O, adapter-integration RED-phase semantics | | `nw-tdd-methodology-paradigm` | write a unit/acceptance test | writing a unit or acceptance test — property-based + state-delta mandate, applicability matrix, debt-payoff curve, delta-first trigger/bypass | | `nw-tdd-methodology-pbt-deep` | write a PBT (deep) | writing a property-based test needing deep mechanics — A13/P6 stateful preconditions, four property-finding strategies, two shrinking mechanisms, targeted/search-based PBT | ## How to use 1. Identify the job in play (which trigger fires). 2. Read `~/.claude/skills/nw-tdd-methodology-{module}/SKILL.md` for that job. 3. For a full DELIVER cycle you will typically load `-cycle` + `-paradigm`; add `-port-to-port`, `-test-doubles`, `-walking-skeleton`, or `-pbt-deep` as the boundary/double/WS/PBT decision arises. The seven modules together cover everything this skill held before decomposition — zero knowledge lost.