Borrowing it
Nothing to install: this file belongs to bskimball/tanstack-hono. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/bskimball/tanstack-hono/master/.agents/skills/vitest/SKILL.mdgit clone --depth 1 https://github.com/bskimball/tanstack-honoWrote 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/bskimball/tanstack-hono/vitest)<a href="https://agentmods.dev/skills/bskimball/tanstack-hono/vitest"><img src="https://agentmods.dev/badge/skills/bskimball/tanstack-hono/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/bskimball/tanstack-hono/vitest"><img src="https://agentmods.dev/badge/skills/bskimball/tanstack-hono/vitest.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00036 | $0.00746 |
| Opus 5.5 | $0.00014 | $0.00298 |
| Sonnet 5.5 | $0.00007 | $0.00149 |
| Haiku 4.5 | $0.00004 | $0.00075 |
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 1mo 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.
This is a copy
92% identical to vitest — 54 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 53 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Vitest is a next-generation testing framework powered by Vite. It provides a Jest-compatible API with native ESM, TypeScript, and JSX support out of the box. Vitest shares the same config, transformers, resolvers, and plugins with your Vite app.
Key Features:
- Vite-native: Uses Vite's transformation pipeline for fast HMR-like test updates
- Jest-compatible: Drop-in replacement for most Jest test suites
- Smart watch mode: Only reruns affected tests based on module graph
- Native ESM, TypeScript, JSX support without configuration
- Multi-threaded workers for parallel test execution
- Built-in coverage via V8 or Istanbul
- Snapshot testing, mocking, and spy utilities
The skill is based on Vitest 3.x, generated at 2026-01-28.
Core
| Topic | Description | Reference |
|---|---|---|
| Configuration | Vitest and Vite config integration, defineConfig usage | core-config |
| CLI | Command line interface, commands and options | core-cli |
| Test API | test/it function, modifiers like skip, only, concurrent | core-test-api |
| Describe API | describe/suite for grouping tests and nested suites | core-describe |
| Expect API | Assertions with toBe, toEqual, matchers and asymmetric matchers | core-expect |
| Hooks | beforeEach, afterEach, beforeAll, afterAll, aroundEach | core-hooks |
Features
| Topic | Description | Reference |
|---|---|---|
| Mocking | Mock functions, modules, timers, dates with vi utilities | features-mocking |
| Snapshots | Snapshot testing with toMatchSnapshot and inline snapshots | features-snapshots |
| Coverage | Code coverage with V8 or Istanbul providers | features-coverage |
| Test Context | Test fixtures, context.expect, test.extend for custom fixtures | features-context |
| Concurrency | Concurrent tests, parallel execution, sharding | features-concurrency |
| Filtering | Filter tests by name, file patterns, tags | features-filtering |
What ships with it
17 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.
- GENERATION.md 136 B
- references/advanced-environments.md 4.2 KB
- references/advanced-projects.md 4.9 KB
- references/advanced-type-testing.md 4.5 KB
- references/advanced-vi.md 4.5 KB
- references/core-cli.md 3.3 KB
- references/core-config.md 3.4 KB
- references/core-describe.md 3.4 KB
- references/core-expect.md 4.6 KB
- references/core-hooks.md 4.4 KB
- references/core-test-api.md 3.9 KB
- references/features-concurrency.md 4.1 KB
- references/features-context.md 4.3 KB
- references/features-coverage.md 3.4 KB
- references/features-filtering.md 3.5 KB
- references/features-mocking.md 4.7 KB
- references/features-snapshots.md 3.5 KB
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.
- 1mo ago First seen · 53 lines · 36 tokens per session scan A 87c8cf025987
vitest is a skill published in the GitHub repository bskimball/tanstack-hono (119 stars, last pushed 1mo ago), licensed MIT. It adds 36 tokens to every session and 746 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 92% identical to vitest, differing in 54 lines, and is treated as a copy.
Other skills, from other repositories
typescript
TypeScript strict mode with eslint and jest.
jest-unit
Unit testing skill using Jest for TypeScript and JavaScript, covering mocking, spies, snapshots, coverage, async testing, and custom matchers.
Jasmine Testing
BDD-style JavaScript testing with Jasmine covering spies, async patterns, custom matchers, clock manipulation, and comprehensive test organization for frontend and Node.js applications.
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".
jest
Jest testing best practices for JavaScript and TypeScript applications, covering test structure, mocking, and assertion patterns.
typescript-testing
Applies repository-aware TypeScript test design, behavior evidence, isolation, and mock-boundary criteria. Use when writing or reviewing unit tests.