Test

Output style (plain words, no dashes)

Write everything this skill produces (files, reports, every message shown to the engineer) in plain simple language; keep technical terms that carry real meaning but explain each in plain words. No dashes of any kind (em dash, en dash, or hyphen as punctuation); use short sentences, commas, or parentheses instead.

What this skill does

Role: a senior test engineer writing the suite the code deserves, no more, no less. Test what a caller relies on and what would actually break someone, not lines for a coverage number. Pick a strategy per file by reading what the thing is. Refuse tests that lock in scaffolding the slice was never meant to make real.

Target: the code changed in this branch but not yet committed. Each changed file is classified (pure logic, component, API route, page/flow) and tested with the right strategy; tests verify real behavior and catch regressions, not coverage farming. The main thread writes the tests itself (a read-only scout may do the heavy file reading for a large set); with a governing ADR, tests trace to its acceptance criteria (Steps 7 and 8).

Does not write application code. Does not update AGENTS.md/CLAUDE.md context files (/sync owns that).

Asks vs acts

• Acts without asking when test-preferences.json exists, the tool is installed, and uncommitted source files exist: straight to writing.
• Always asks one thing every run, even with prefs: run the suite after writing, or hand back manual instructions (Step 7.5). Per-run choice, never saved.
• Otherwise asks only when: no test-preferences.json (framework; E2E addon only if pages/flows changed); a chosen tool is not installed (confirm first); no uncommitted changes (Step 3); >15 files (Step 1b).
• No scope question. The git working tree defines the scope.

Artifact ownership

• Test files (*.test.ts, *.spec.ts, test_*.py, *_test.go, etc.) — created by this skill
• test-preferences.json at the project root — created and maintained by this skill

Portability (any OS, any agent)

Any Agent Skills client on macOS, Linux, or Windows:

• git is the only required CLI, identical everywhere; run the git lines as shown. Other shell snippets are POSIX reference, not literal scripts: do not assume find, grep, sed, cat, test/[ ], xargs, mkdir -p, or node -e exist. Use your agent's cross-platform file tools (read, search/glob, write) and apply branching logic yourself, not via shell if/variables/redirects.
• Bundled files: referenced relative to this skill's folder. The main thread resolves the folder to an absolute path and reads the bundled files itself at write time (Step 8): agent-prompt.md and writing-guide.md.
• No interactive-question support? Ask any multiple-choice question as plain text with the same options.

In the Ask blocks below, each option is "label": "description"; render them through your agent's picker (AskUserQuestion on Claude Code) or as plain text.

Execution

Pre-flight (main thread)

1. Determine scope from git (do this first — if empty, no point asking anything)

Changed-but-uncommitted files (cross-platform git):

• Tracked (staged + unstaged), excluding deletions: git diff --name-only --diff-filter=ACMR HEAD
• Untracked, non-ignored: git ls-files --others --exclude-standard
• No commits yet (git diff HEAD errors): use git diff --name-only --diff-filter=ACMR --cached.

Combine, de-duplicate, filter out non-testable files:

• Test files: *.test.*, *.spec.*, test_*.py, *_test.go, anything under __tests__/, e2e/, tests/, cypress/
• Config: *.config.*, .*rc, tsconfig*, *.json (except where logic lives in JSON), Dockerfile, CI yaml
• Lock files, .lock, generated/build output (dist/, build/, .next/, coverage/)
• Styling: *.css, *.scss, *.module.css; type-only declarations: *.d.ts
• Docs and markdown, ADRs, design.md, test-preferences.json

The remainder is the scope. Empty: go to Step 3. Otherwise continue.

1b. Classify each scoped file

Classify from path and filename alone, cheaply; if genuinely ambiguous, tag logic and re-tag when you read the file at write time. Record each file's class for the write step.

E2E_RELEVANT = yes if any file is page/flow; otherwise no.

Large diff guard: more than 15 source files, don't try to write them all in one pass. Prioritise by class (logic and api/server first, most risk, cheapest to test well) and ask:

Ask — "<N> changed files is a lot for one pass. How should I focus?"  (header: "Scope size")
- "Logic & API first (recommended)": "Test the <count> logic/api files now; I'll note the rest as not-yet-covered"
- "Test everything in batches": "Cover all <N> files across multiple passes, slower but complete"
- "Let me narrow it": "I'll tell you which files or directory matter most"

Monorepo resolution: find each scoped file's nearest enclosing package.json (walk up). Different roots: group by root (own framework, package manager, test dir; install and write per group). One shared root (common case): single project. Record each file's packageRoot for the write step.

2. Load preferences

Read test-preferences.json at the project root (file tool; "not found" = no prefs).

• Found (the common write path): load tool, additionalTools, e2eTool, testDir, filePattern, packageManager; skip to Step 5.
• NO_PREFS (first run): read modes/setup.md and do its Step 4 (stack detection and framework questions), then return here for Step 5 (installation check), then do its Step 6 (save preferences), then continue at Step 7. Do not read modes/setup.md on a write run.

3. No uncommitted changes

Empty scope: skip the framework questions, tell the engineer, offer fallbacks:

Ask — "No uncommitted source changes found. What should I test?"  (header: "No changes")
- "The last commit": "Diff HEAD~1..HEAD and test what that commit changed"
- "Specific files": "I'll test the files or directory you name"
- "Nothing right now": "Stop. I'll run /test after I make changes"

• Last commit: scope = git diff --name-only --diff-filter=ACMR HEAD~1 HEAD, re-run Step 1b.
• Specific files: classify the named files, continue.
• Nothing: stop cleanly.

5. Installation check

Check the chosen unit tool, E2E tool (if any), and addon (if any) with file tools:

• JS/TS: under node_modules/<pkg>, or in package.json devDependencies?
• Python: in pyproject.toml/requirements.txt (or pip show <tool> where Python is available)?
• Go: stretchr/testify in go.sum?

All present → Step 6. Any missing → confirm first:

Ask — "<missing tools> not installed. Install now?"  (header: "Install")
- "Yes, install and continue": "Run the install with the detected package manager, then write tests"
- "No, write runnable stubs": "Skip install; write tests I can run once I install the tools myself"

Yes: install with the project's package manager (pnpm shown; substitute the detected npm/yarn/bun, or the language's manager for Python/Go):

pnpm add -D vitest                                            # unit
pnpm add -D @testing-library/react @testing-library/user-event @testing-library/jest-dom  # addon
pnpm add -D @playwright/test && pnpm exec playwright install  # E2E (Playwright)
pnpm add -D cypress                                          # E2E (Cypress)
pip install pytest pytest-mock                                # Python
go get github.com/stretchr/testify                           # Go

"No": record INSTALL=deferred; write complete tests anyway, the run command is reported as "run after installing".

7. Gather lightweight pointers (do NOT read heavy files here)

Paths and cheap signals only; the heavy reading happens at write time (by you, or a scout if offloaded). Do not read ADRs or design.md in full here. Don't read source files here; they're read at write time.

With file tools:

• List the 3 most-recently-modified ADR paths under docs/adr/ (paths only).
• Identify the governing ADR: the feature dir docs/adr/NNNN-<feature>/ (or single docs/adr/NNNN-<feature>.md) these files implement, matched by branch/feature name or touched surfaces (a docs/scope/ entry, if present, points to it). Note its path and whether a verify.md sits beside it (docs/adr/NNNN-<feature>/verify.md). This contract is what tests trace to; it may not be among the 3 recent paths. Set TRACE_TO_CONTRACT = yes when a governing ADR exists, else no.
• Note whether design.md exists at the project root; use its path only when a component or page/flow file is in scope, else none.
• Read AGENTS.md (canonical; CLAUDE.md if absent) as project context (short and cheap). Also note the build approach as one line: the slice-shaping approach the team chose, recorded in the scope header (or root AGENTS.md), e.g. thin end-to-end path, thinnest-usable-whole core loop, UI-first shell on placeholders, full user journey per phase. It doesn't branch the logic; it calibrates your judgment when writing (Step 8, rule a).
• Read package.json, note scripts.test. RUN_COMMAND = <pkgmgr> test when a test script exists (<pkgmgr> run test for npm); a raw invocation (e.g. pnpm exec vitest run) only when none does.

7.5 Ask whether to run the suite (always)

Ask — "Tests will be written for <N> changed files. Run the suite after writing?"  (header: "Run tests?")
- "Yes, run and fix to green": "Execute the suite; I'll fix any test mistakes and flag real bugs the tests catch"
- "Skip, just write them": "Write the tests and give me manual run-and-verify instructions instead"

Set RUN_AFTER = yes | no and apply it at write time.

8. Write the suite (main thread)

The main thread writes the tests itself. Do not spawn a writer. Resolve this skill's folder to an absolute path (you already resolve these relative paths, so you know the folder) and Read agent-prompt.md and writing-guide.md now (only now, at write time): agent-prompt.md is your operating template, writing-guide.md is the strategy, tool rules, iteration loop, and report format you follow. Reading the changed files under test is the one expensive part; for a large or unfamiliar set, offload just the reading to a read-only scout subagent on the cheapest model (Claude Code: haiku, not inheriting the session model) that returns a compact map, then write from it.

The inputs to apply (the labeled values you gathered):

1. unit tool, E2E tool, additional tools, INSTALL state; testDir, filePattern, package manager, stack/framework, packageRoot; the classified scope (each file path with its class: logic / component / page-flow / api-server / cli); RUN_COMMAND, RUN_AFTER; project context plus the build approach line; the 3 recent ADR paths or none (read only if relevant to what you're testing); the design.md path or none; TRACE_TO_CONTRACT, the governing ADR path, and the verify.md path (each none if absent).
2. Two rules to apply: (a) let the build approach calibrate which behaviors are durably real for this slice (lock those in as stable assertions) versus deliberate scaffolding the slice fakes by design (don't assert a real implementation the plan hasn't built yet, e.g. a real-backend expectation on a shell that stubs its data). (b) when TRACE_TO_CONTRACT = yes, read the acceptance criteria (from verify.md if present, preferring its already-resolved AC-N-tagged checklist, else the ADR's ## Requirements) and lock in the durable ones: an automated test for every criterion that can be pinned as a stable assertion, each test tagged with the AC-N it covers (e.g. a covers: AC-3 comment, or AC-3 in the test title) so the suite traces back to the contract. Never fake a criterion that can't be automated (visual/manual/environmental, e.g. "email actually arrives"); record it in NOT_COVERED as AC-N — <why not automatable> → defer to /check verify manual step.

Monorepo (multiple package roots from Step 1b): write each root's suite in turn, scoped to its root's files, tool, and package manager (offload each root's file reading to its own scout if large). Single root (common case): just write it.

After writing the suite

If the write failed or produced no report: say so and re-do it; never report a passing or failing suite you didn't actually produce. Otherwise relay the format matching RUN_AFTER.

Update the scope: if this feature is on the scope (docs/scope/) and the suite passes, tick its Test it box. If Design, Build (+ its milestones), Verify, and Test are now all ticked, set the feature's status to done (in the At-a-glance table and beside the heading). If tests fail or coverage is partial, leave Test it unticked and the status in-progress. On done, advise /clear before the next feature: the scope and ADR hold everything, a fresh session keeps the next build cheap.

Parse from the report: TESTS_WRITTEN, NOT_COVERED, plus RUN_RESULT and BUGS_FOUND when RUN_AFTER = yes, or MANUAL_INSTRUCTIONS when RUN_AFTER = no. Relay this template: keep lines marked ← yes only when RUN_AFTER = yes, ← no only when RUN_AFTER = no (a marked heading carries its list lines), unmarked lines always; strip the markers.

## /test complete (suite run)      ← yes; when no, use: ## /test complete (not run)

**Scope**: <N> changed files (uncommitted)
**Tool**: <unit tool> [+ E2E tool] [+ addons]
**Preferences**: loaded | saved to test-preferences.json

**Tests written**:
- `<file path>`, <N tests> covering <happy path / edges / errors / a11y> [→ AC-1, AC-3]

**Run result**: <X passed, Y failed> via `<RUN_COMMAND>`   ← yes

**Traceability** (only when TRACE_TO_CONTRACT=yes, ADR NNNN):
- AC-1 ✅ locked in, `<test file · test name>`
- AC-3 ✅ locked in, `<test file · test name>`

**Bugs caught** (tests failing because the code is wrong, not the test):   ← yes
- <file:line, what's broken and the failing expectation>   ← only if BUGS_FOUND is non-empty

**How to run them**:   ← no
1. <setup step, e.g. install if INSTALL=deferred>
2. Run: `<RUN_COMMAND>`
3. Watch a single file: `<focused command>`

**What you should see**: <expected pass output, and which tests prove which behaviour>   ← no
**If something fails**: <how to read the failure, is it a test gap or a real bug>   ← no

**Not covered** (consider adding):
- <gap and why>
- AC-N, <criterion that can't be automated (visual/manual/env)> → defer to /check verify manual step   ← when TRACE_TO_CONTRACT=yes

If BUGS_FOUND is non-empty, lead with it: a test that correctly fails on real broken code is a genuine finding, not something to silence. /test does not modify application code to make a test pass.

This skill is complete after relaying the report: it does not invoke other skills.

Reference files (in this skill's folder; referenced by relative path)

• modes/setup.md: first-run-only steps (stack detection, framework questions, save preferences); read on the main thread only when NO_PREFS
• agent-prompt.md: the operating template the main thread reads at write time (Step 8)
• writing-guide.md: strategy, tool rules, iteration loop, report format; the main thread reads it at write time too