Skill: plan-tests

Turns an already-specified feature into a test plan: a table that ties every acceptance criterion in spec.md §5 to at least one named test, the levels those tests live at (unit / integration / e2e / contract / load), the integration strategy (a real dependency, spun up throwaway), and the test-data + cleanup approach. The plan is written before a single test exists — the next stage, implement, reads this map and writes the red tests against it, not "however it seems". This file is the spine; the output scaffold lives in templates/test-plan.md.

This skill keeps only its own machinery. Question phrasing is shared → ../_shared/ask-style.md. Depth (inline in the spec vs a separate file) follows the size matrix → ../_shared/size-matrix.md. It names test levels, never test tools — the concrete commands are detected by implement against the repo, not hard-coded here.

Plan prose follows artifact_language — the ## Test plan heading (parsed downstream), test names and level tokens stay English → ../_shared/artifact-language.md.

Owner

QA + the engineer who will implement the feature (co-authors). QA drives the level breakdown and the edge/error cases; the implementing engineer confirms each acceptance criterion has a reachable test and that the integration strategy fits the repo. The Tech Lead signs off that no acceptance criterion is left uncovered.

Inputs

• <slug> — the same feature slug every earlier stage used.
• Gate (hard-refuse if missing): docs/features/<slug>/spec.md. Its §5 acceptance criteria are the entire reason this plan exists — each one must map to a test. If spec.md is absent → STOP and point: «run specify <slug> first — the test plan maps its §5 acceptance criteria to tests».
• (Optional) docs/features/<slug>/data-model.md — the entity shapes tell you what test data to build and what to seed/clean per suite. Read it if present.
• (Optional) docs/features/<slug>/sad.md §6 sequence diagrams — each drawn flow is an e2e candidate; each cross-participant boundary is a contract-test candidate.
• (Optional) docs/features/<slug>/.size — depth hint. Absent → default to M (separate test-plan.md file) and say so loudly in the handoff — «size M (default — no .size; run /sdd:classify-size <slug>)».

Protocol

1. Gate. test -f docs/features/<slug>/spec.md → fail = refuse with the pointer above. Then read §5 (acceptance criteria — the rows of the coverage table) and §6 (NFRs — which drive load tests). Read data-model.md / sad.md §6 if present.
2. Pick the output target. Per the size matrix: XS/S → write the plan inline in spec.md as a short ## Test plan section (a coverage table is enough — no separate file); M+ → a separate docs/features/<slug>/test-plan.md from the template. Confirm the target with one AskUserQuestion (phrasing per ../_shared/ask-style.md) when .size is absent.
3. Map levels — generic only. Name test levels from a fixed vocabulary, never a tool or language: unit (pure logic — a rule, a calculation, a validator, no I/O), integration (the module against a real dependency it owns — DB, cache, queue), e2e (a full flow end to end, one per critical user story), contract (a boundary between two participants — an API shape or an event schema agreed by both sides), load (only when an NFR carries a number — throughput, p95 latency). When sad.md frontmatter target_surfaces declares a UI surface (web-frontend / mobile-app / desktop-app), add the frontend tiers — component (a UI component exercised in isolation), visual-regression (web — the rendered UI diffed against a baseline), e2e-through-UI (the flow driven through the real UI, not just the API). These are the "testing trophy", the dominant frontend testing vocabulary (web.dev / Kent C. Dodds) — a vocabulary, not a mandate (→ ../_shared/surfaces.md). When the design pipeline ran, source the UI rows from its artifacts: the e2e-through-UI path comes from ux-flows.md (the flow is the test's script) and the states a component test must cover come from screens.md (the manifest's state rows). Do not write tool names (no specific test runner, broker, visual-regression, or load tool) — implement detects what the repo already uses (e.g. Playwright / Storybook / a visual-diff tool).
4. Core mapping (the contract of this skill) — user chooses the level per AC. Build the AC→test table: every acceptance criterion in §5 maps to ≥1 test. For each AC, propose a default level from a heuristic (pure logic/rule/validator → unit; behaviour against a real dependency the module owns → integration; a full user-story flow → e2e; a cross-participant API/event shape → contract; and — when a UI surface is declared — a UI piece → component, a user-facing flow → e2e-through-UI), then confirm the level(s) with the user via one AskUserQuestion (multiSelect — an AC may fan out to several levels, e.g. unit for the rule + e2e for the flow), phrased per ../_shared/ask-style.md. The user's choice is authoritative and is recorded in the table's Level column; implement reads it to write the test at the right level (it does not re-decide). A criterion with zero tests is the cardinal anti-pattern. Name each test descriptively from the criterion's intent (e.g. over-quota request is rejected), not from any framework convention.
5. Edge cases & error paths. Every error/authorization acceptance criterion gets its own dedicated test row — never folded into the happy path. List the boundary and failure cases the spec implies (missing identifier, malformed input, dependency unavailable → the spec's fallback behaviour) as explicit rows with their expected outcome named in plain words (no status numbers, no error-code strings).
6. Integration strategy — real, ephemeral dependency. For integration tests, the default is an ephemeral real dependency, e.g. a throwaway DB container spun up for the suite and torn down after (testcontainers-style). Mocking the datastore is an anti-pattern — a passing mock is not a passing production. State the seed strategy (factories/fixtures for the data shape) and the cleanup boundary (per-test vs per-suite); without cleanup the suite goes flaky and blocks CI.
7. NFR → load. For each §6 NFR that carries a number, write one concrete load scenario (target rate, duration, the metric and its threshold) and name the tool generically: the load tool already in your repo, or e.g. k6 or Locust. If no NFR carries a number, mark the load section <!-- N/A: no numeric NFR --> — do not invent a load test.
8. CI placement. Note which suites run where: fast suites (unit, contract) on every PR; the heavier ones (e2e, load) on a schedule or pre-release. The split is advice, not a pipeline config — implement and the repo's CI own the actual wiring.
9. Socratic walk + write. Walk the coverage table and the strategy choices with the 4-state actions from ../_shared/ask-style.md (Accept / Fix / Save-as-OQ / Drop); on Fix, regenerate that one row (one round, second answer final). Maintain the edits-log per ../_shared/socratic-loop.md. On pass, write the plan to its target (separate file for M+, inline ## Test plan for XS/S).
10. Structural self-check — per ../_shared/self-check.md: re-read the written plan from disk and verify 6 items: (1) every spec.md §5 AC id appears in the coverage table; (2) every error/authorization AC has its own dedicated row (not folded into a happy path); (3) every Level value ∈ the fixed vocabulary {unit, integration, e2e, contract, load, component, visual-regression, e2e-through-UI}; (4) zero tool names in the plan (no runner / broker / visual-diff / load-tool name outside the single "e.g. k6 / Locust" allowance); (5) the load section carries numbers (rate + duration + metric + threshold) or the literal <!-- N/A: no numeric NFR -->; (6) the plan sits at its size-correct target (inline ## Test plan for XS/S or route quick, separate test-plan.md for M+). Fix + re-check ≤2 cycles; surface anything unresolved.
11. Propose commit + handoff. test-plan: <slug>. Then emit the stage-handoff block per ../_shared/handoff.md — What I did (incl. «self-check: 6/6 pass») + Review (test-plan.md, or spec.md ## Test plan for XS/S) + Run next (/clear, then /sdd:implement <slug>, which consumes this map to write the red tests).

Definition of Done

• The plan exists at its size-correct target: a separate docs/features/<slug>/test-plan.md for M+, or an inline ## Test plan section in spec.md for XS/S.
• Every acceptance criterion in spec.md §5 maps to ≥1 named test — zero uncovered criteria.
• Each error / authorization criterion has its own dedicated test row, not folded into a happy path.
• Test levels are generic (unit / integration / e2e / contract / load; + component / visual-regression / e2e-through-UI when a UI surface is declared in target_surfaces) — no test-runner, broker, visual-regression, or load-tool name is hard-coded (the load tool is named only as "the one in your repo, or e.g. k6 / Locust"; UI tools are detected by implement).
• Integration tests use an ephemeral real dependency (throwaway container), with the seed and cleanup boundary stated; no mocked datastore.
• Every numeric §6 NFR has a load scenario (rate + duration + metric + threshold), or the load section is explicitly <!-- N/A -->.

Anti-patterns

• An acceptance criterion with no test. The whole point of the map is that §5 is verifiable; an uncovered criterion means it isn't.
• Naming a concrete tool or language — a specific runner, broker, or load tool. The legacy plan hard-coded k6; here load is "the tool already in your repo, or e.g. k6 / Locust", and the rest stay generic levels. implement detects the real commands.
• Mocking the datastore. A passing mock is not a passing production — use a throwaway real dependency for integration.
• e2e without a cleanup boundary. Leftover state makes the suite flaky and every flaky run blocks CI.
• "100 % coverage" as the goal. The target is critical paths + happy + error paths mapped to acceptance criteria, not a line-count number.
• A wishlist plan — "would be nice to add". A test plan is a commitment the next stage executes, not a backlog.
• Inventing a load test with no numeric NFR. No number → <!-- N/A -->, not a fabricated throughput target.

References & template

• ../_shared/ask-style.md — canonical question/option phrasing for steps 2 and 9.
• ../_shared/self-check.md — the structural self-check contract step 10 runs.
• ../_shared/size-matrix.md — inline-in-spec (XS/S) vs separate file (M+) depth.
• ../_shared/surfaces.md — a declared UI surface adds the component / visual-regression / e2e-through-UI tiers (testing-trophy vocabulary); read from sad.md target_surfaces.
• ./templates/test-plan.md — output scaffold: AC→test mapping table, generic test levels, ephemeral-dependency integration strategy, stack-agnostic load section. Its <!-- … --> comments are the per-section contract.