Outside-In TDD Methodology

LANGUAGE CONVENTION FRAME (read FIRST — overrides all examples below)

Code examples in this skill use Python syntax for illustration only. They are NOT prescriptive about target language. nWave is language-agnostic per the "genericity and agnosticism" mandate (2026-05-24).

Before applying TDD cycle, detect the target project's language from manifest files: package.json → TypeScript/JS (jest/vitest); Cargo.toml → Rust (cargo test/proptest); go.mod → Go (testing/ginkgo); pyproject.toml/setup.py/Pipfile → Python (pytest/hypothesis); pom.xml/build.gradle → Java/Kotlin (JUnit5/jqwik); *.csproj/*.fsproj → C#/F# (xUnit/FsCheck); Gemfile → Ruby (RSpec); Package.swift → Swift (XCTest/swift-testing).

When the target language is NOT Python: adapt EVERY code example — replace Python imports, type hints, class/function syntax, test-framework specifics with target equivalents. Project conventions ALWAYS WIN over skill examples.

Empirical anchor: skill examples being Python-only caused LLM to emit Python code in greenfield TS project despite language-agnostic mandate. Fix per F-SKILL-EXAMPLES-LANGUAGE-LEAK. Connects [[feedback_language_adapter_plugin_architecture_2026_05_24]].

TDD cycle — 3-phase canonical (ADR-025, 2026-05-07)

Current canonical: DELIVER cycle is 3-phase: RED → GREEN → COMMIT.

• RED absorbs PREPARE + RED_ACCEPTANCE + RED_UNIT (legacy 5-phase). Writes PBT unit tests targeting production code; unskips the corresponding AT scenario authored upstream by DISTILL. Exits via the fail-for-right-reason gate — both PBT unit + AT must fail with a semantically-correct error (AssertionError / expected-exception-not-thrown), not a collection error / import error / skip marker. The gate preserves RED→GREEN discipline atomically without separate phase boundaries.
• GREEN: implement minimum production code making PBT unit + AT pass. Exit gate all-tests-pass.
• COMMIT: commit this step's owned files via des-commit (carries the Step-Id: trailer and is parallel-safe — see issue #51 / ADR-027), not raw git add/git commit. F-DES-COMMIT-PHASE-CRAFTER-DEAD-PATH guidance in commit.yaml addresses adapter-probe annotation requirement.