Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add PaulRBerg/agent-skills --skill vitestgit clone --depth 1 https://github.com/PaulRBerg/agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/paulrberg/agent-skills/vitest)<a href="https://agentmods.dev/skills/paulrberg/agent-skills/vitest"><img src="https://agentmods.dev/badge/skills/paulrberg/agent-skills/vitest/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/paulrberg/agent-skills/vitest"><img src="https://agentmods.dev/badge/skills/paulrberg/agent-skills/vitest.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00041 | $0.00599 |
| Opus 5 | $0.00020 | $0.00300 |
| Sonnet 5 | $0.00008 | $0.00120 |
| Haiku 4.5 | $0.00004 | $0.00060 |
Grade A, and why
vitest 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 10d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Vitest
Follow the repository's Vitest configuration and test conventions before introducing generic patterns.
Workflow
- Inspect package scripts, Vitest config/projects, setup files, neighboring tests, path aliases, environment selection, and repository instructions.
- Define the behavior or regression the test must prove. Prefer public behavior and observable outcomes over implementation details.
- Match local file placement, naming, imports/globals, fixtures, cleanup, DOM utilities, and assertion style. Do not enable globals, jsdom, coverage, or new setup merely because they are common defaults.
- Load conditional guidance only when needed:
- components, async behavior, snapshots, type tests, tables, fixtures, tags: references/testing-patterns.md;
- spies, module mocks, timers, environment stubs: references/mocking.md;
- config, projects, environments, coverage, reporters, v4 migration: references/configuration.md;
- timeouts, flaky tests, mock failures, resolution errors: references/troubleshooting.md.
- Run the narrowest established command for the changed file or test name, then the affected package suite when shared
setup or contracts changed. Use
nlx vitest run ...only when the repository has no preferred recipe/script. Prefer--reporter=agenton Vitest 4.1+ for minimal agent-friendly output when the repository has no reporter convention.
Defaults
- Colocate tests when the repository does.
- Restore mocks, timers, environment, and mutable shared state using the local cleanup convention.
- Mock system boundaries, not the behavior under test.
- Add coverage configuration only when coverage is the requested outcome.
- Do not use jest-dom matchers unless setup imports
@testing-library/jest-dom. - In Effect-TS repositories, follow
@effect/vitestconventions (it.effect, Layers, TestClock) instead of generic patterns. - For a bug fix, reproduce the failure before relying on the passing result when practical.
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 10d ago First seen · 48 lines · 41 tokens per session scan A 50cd5eca47e5
vitest is a skill published in the GitHub repository PaulRBerg/agent-skills (70 stars, last pushed today), licensed MIT. It adds 41 tokens to every session and 599 once invoked, about $0.0002 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 2026-08-30.
Other skills, from other repositories
typescript
TypeScript strict mode with eslint and jest.
jest
Jest testing best practices for JavaScript and TypeScript applications, covering test structure, mocking, and assertion patterns.
jest-unit
Unit testing skill using Jest for TypeScript and JavaScript, covering mocking, spies, snapshots, coverage, async testing, and custom matchers.
raise-coverage
Input: a package directory (for example packages/txpool) and optionally a target line-coverage percentage. Without a target, raise every threshold by five points or to what the new run measures, whichever is lower.
typescript-testing
Applies repository-aware TypeScript test design, behavior evidence, isolation, and mock-boundary criteria. Use when writing or reviewing unit tests.
vitest-skill
Generates Vitest tests in JavaScript/TypeScript with Vite-native speed. Jest-compatible API with ESM support and HMR. Use when user mentions "Vitest", "vi.mock", "vitest.config". Triggers on: "Vitest", "vi.mock", "vi.fn", "Vite test", "vitest config".