whiteboard: Skill for Claude Code

.claude/skills/testing-techniques/SKILL.md

testing-techniques is a skill for Claude Code from kamiazya/whiteboard. It costs 213 tokens per session (1,894 once invoked), scanned A, original, Apache-2.0.

A catalogue of techniques for writing reliable automated tests with Vitest, a JavaScript and TypeScript test tool. It covers async checks, fake time, browser tests, mocks, isolation, property-based tests, and mutation testing.

In plain words
What is it for?
Use it to choose test techniques, check test stability with repeats and stress runs, and improve what tests prove in a whiteboard repository.
Why use it?
It helps prevent tests that pass alone but fail during a full parallel run, or stay green without checking the intended behaviour. It also describes ways to find flaky and weak tests before sharing changes.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

This is kamiazya/whiteboard's own configuration. It tells Claude Code how to work on whiteboard itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything whiteboard configures →

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is node .claude/scripts/flake-watch.mjs # tests failing ≥2 main runs in 14 days.

Part of the whiteboard plugin — 21 skills, 18 agents, 3 hooks shipped together

Reuse

Borrowing it

Nothing to install: this file belongs to kamiazya/whiteboard. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/kamiazya/whiteboard/main/.claude/skills/testing-techniques/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/kamiazya/whiteboard

Made for: Claude Code.

Or install whiteboard, the plugin that ships this one along with the rest of its 21 skills, 18 agents, 3 hooks.

Wrote this? Show the measurements

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README.md
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Per session 213 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,894 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00213 $0.01894
Opus 5 $0.00106 $0.00947
Sonnet 5 $0.00043 $0.00379
Haiku 4.5 $0.00021 $0.00189

Measured today against content hash af5af12672b1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

testing-techniques scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/testing-techniques/SKILL.md · 97 lines

How it starts

The opening of the file, as written. The whole thing — 97 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Testing techniques (whiteboard)

test-layer-selection answers where a test goes. This skill answers how to write one that stays green and how to know it asserts something. The body here is an index; the detail is in resources/*.md, opened one at a time for the situation at hand — never all at once.

The rung ladder

Every technique here sits on a rung, and the rung is chosen by what would actually catch the mistake — strongest first:

Rung Catches the mistake… This repo's instruments
executable at lint / typecheck / test time, mechanically tools/biome-plugins/test-flake-shapes.grit (rules read from the file by its guard), tools/arch-lint's test scans (lazy imports, duplicate titles, the sleep ledger), guard tests (browser-test-name-length, vitest-data-dir, local-node-version)
setup guard at runtime, for every test in a project apps/web/vitest.setup.ts (cleanup, fake-timer leak, localStorage), browser-setup.ts (stylesheet, async budget), sharedBrowserTestConfig (trace bounds)
review criteria when a reviewer reads the diff review-gate/resources/test-coverage.md
prose only if someone remembers integrator-flow.md's CI-flakes section (the measurements), this skill

A shape that costs a real defect twice earns a higher rung. How to move one up is resources/executable-rungs.md.

The resources describe the INSTALLED vitest — the vitest: line of pnpm-workspace.yaml's catalog (5.0.0 since 2026-09-05). A config key the installed version does not know is ignored silently, so check the version before relying on one. Features newer than a reader's training carry their API and a snippet, beside the situation each serves — never in a file named after a version, which only a reader who already knows the feature opens.

Open the resource for the situation

Situation Resource
naming a test or a file, a duplicate title, a fixed sleep, a count or ordinal in a title resources/naming-and-structure.md
async assertions, expect.poll, waitFor, fake timers, clocks, scheduler teardown resources/async-and-timers.md
a .browser.test.tsx: focus, typing, locators, timeouts, titles, traces resources/browser-mode.md
mocks, module state, storage, data dirs, workers, --project filters resources/isolation-and-state.md
a property test, a Stryker survivor, a generator that reaches nothing, a coverage ledger resources/property-and-mutation.md
"is this test stable?" — repeats, stress, isolation vs full run, quarantine, flake-watch resources/stability-checks.md
adding a GritQL shape, a setup-file guard, or a source-scan test resources/executable-rungs.md
projects and filters, pools and caches, .vitest/ artifacts and reporters, benchmarks, custom matchers, coverage — and the four tempting options measured and REFUTED here resources/configuration.md
moving to a new vitest major: breaking changes measured against this tree, and the order to land them resources/vitest-upgrade.md

Read the full file on GitHub · 97 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. today First seen · 97 lines · 0 tokens per session scan A af5af12672b1

Subscribe to this mod's changes

testing-techniques is a skill published in the GitHub repository kamiazya/whiteboard (6 stars, last pushed today), licensed Apache-2.0. It adds 213 tokens to every session and 1,894 once invoked, about $0.0011 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-06.