feat(skills): tdd-criteria skill v0.1.0 [TDD-default + 4 carve-outs + 4 anti-loophole rules incl. test-immutability]

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

skills/tdd-criteria/SKILL.md

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+---
+name: tdd-criteria
+version: 0.1.0
+description: >
+  TDD by default with four bright-line carve-outs. Applies before any code
+  change the agent didn't author this session. Triggers: "TDD",
+  "test-driven", "следуй TDD", "use TDD", "should I write tests",
+  "skip tdd", "[skip-tdd: ...]", "[test-modify: ...]", "tdd-criteria".
+  Cross-agent policy — no tool refs. Full rationale:
+  .wiki/concepts/tdd-criteria-design.md
+---
+
+# tdd-criteria
+
+> TDD by default. Skip only with a bright-line marker. Tests defend code from silent deletion; rule 4 defends tests from silent rewriting.
+
+## When this runs
+
+**At session start** — when `CLAUDE.md` contains the line `follow tdd-criteria`.
+
+**Before any code change** the agent didn't author this session — touching a `*.ts`, `*.js`, `*.py`, or similar source file triggers the decision algorithm below.
+
+**On explicit reference** — when the user says "TDD", "test-driven", "следуй TDD", "use TDD", "should I write tests", "skip tdd", "tdd-criteria", or includes `[skip-tdd: ...]` or `[test-modify: ...]` in a commit subject.
+
+## Default mode
+
+TDD by default. Skip only if one of four bright-line carve-outs matches and is marked in the commit subject.
+
+## Decision algorithm (8 questions, top-down)
+
+Walk through in order. First «yes» determines mode. All «no» → TDD by default.
+
+1. **Bug fix?** → TDD (red-test first)
+2. **Consuming external contract** (SDK, REST API, чужая schema)? → TDD (contract-test)
+3. **Security / auth / money / identifiers?** → TDD
+4. **Pure logic** — function (input → output) without I/O, global state, bounded inputs? → TDD
+5. **Visual / config** — CSS, layout, design tokens, `.env.example`, prompts, wiki, README? → SKIP, `[skip-tdd: visual]`
+6. **Spike** — explicit POC «throwaway» in commit/PR/task subject? → SKIP, `[skip-tdd: spike]` + spike-survivor task if code survives
+7. **One-shot** — migration, ETL backfill, ad-hoc cleanup, runs once? → SKIP, `[skip-tdd: oneshot]`
+8. **Transit wrapper** ≤10 lines — no branching, re-export / glue? → SKIP, `[skip-tdd: wrapper]`
+
+(default) → TDD
+
+## Ironclad rules (TDD obligatory)
+
+1. **Bug fix** — if there's an issue / failure log / repro, write a red-test codifying the repro. Marginal cost: 5 min. Marginal benefit: regression test forever.
+2. **Pure logic, bounded inputs** — no fixtures, no mocks, no setup. Test = input/output pair. Skipping is gratuitous.
+3. **Third-party contract** — SDK bumps change signatures silently. Contract-test pins known input → known shape. Catches break at first install, not days later.
+4. **Security / auth / money / IDs** — asymmetric blast radius: false positive ≪ false negative. TDD = insurance.
+
+In all four, recovery cost from silent deletion is high. The test is the only artefact that makes deletion visible.
+
+## Permissive carve-outs (skip + marker required)
+
+| # | Category | Trigger | Marker |
+|---|----------|---------|--------|
+| 5 | Visual / config | CSS, layout, tokens, `.env.example`, prompts, wiki | `[skip-tdd: visual]` |
+| 6 | Spike | «POC, throwaway» in commit/PR/task subject | `[skip-tdd: spike]` |
+| 7 | One-shot | Migration, ETL, ad-hoc cleanup; runs once | `[skip-tdd: oneshot]` |
+| 8 | Wrapper | ≤10 lines, no branching, re-export / glue | `[skip-tdd: wrapper]` |
+
+These are **accepted-risk zones** — you accept that an agent can vandalise without immediate signal, because recovery is cheap (eyeball next render; throwaway by contract; runs once; reconstruct ≤ delete).
+
+## Anti-loophole
+
+1. **Skip without category is invalid.** One of four explicit categories required — not «other reasons». No marker = violation.
+2. **Spike survivor rule.** Merged spike → same merge-commit creates `[backfill-tests-<slug>]` task. Otherwise «spike» becomes «skipped tests forever».
+3. **Friction is the point.** `[skip-tdd: visual]` 50× in a design-system rework is irritating — that's the fence. Re-evaluate after ≥2 weeks, not before.
+4. **Tests are append-only by default.** Modifying an assertion, deleting a test, or disabling it (`it.skip`/`xit`/`@pytest.mark.skip`/`@Disabled`) requires:
+   - **Marker in commit subject:** `[test-modify: <test-name>: was <X>; is <Y>; reason: <Z>]` — `<X>` and `<Y>` are **literal assertion expressions**, not paraphrased. Example: `[test-modify: validates email: was expect(isValid("a@b")).toBe(true); is expect(isValid("a@b.com")).toBe(true); reason: tightened spec to require TLD]`
+   - **Separate commit from impl changes.** A commit must not modify both `*.test.*` and `src/*` files (or project-equivalents). `git log --grep '\[test-modify'` must show a clean test-only audit trail.
+   - **Why literal was/is:** an agent forced to write the literal assertion publishes exactly what they're rewriting. «Updated to match new behaviour» hides everything — agents will use that whenever allowed.
+
+## Cross-agent applicability
+
+Pure policy — no agent-specific tool references in this body. Works on Claude, Gemini, Copilot, or any future agent. Hermes mapping: `mode: auto`, `category: software-development`, no replace-rules.
+
+## Out of scope
+
+- Does not enforce via git hooks (separate optional task: `tdd-criteria-precommit-hook`).
+- Does not modify project `CLAUDE.md` (that's `project-bootstrap`'s job).
+- Does not run tests.
+- Does not apply rule 4 retroactively to tests written before the rule was adopted.
+
+## Why this exists
+
+Tests make behaviour an invariant; without them, code is an artefact silent-deletable by agents. AND: the test itself must be defended too (rule 4) — otherwise the contract collapses back into an artefact when the agent rewrites the failing test. Full rationale: `.wiki/concepts/tdd-criteria-design.md`.