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 xonovex/platform --skill vitest-guidegit clone --depth 1 https://github.com/xonovex/platformWrote 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/xonovex/platform/vitest-guide)<a href="https://agentmods.dev/skills/xonovex/platform/vitest-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/vitest-guide/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/xonovex/platform/vitest-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/vitest-guide.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 | $0.00071 | $0.00581 |
| Opus 5.5 | $0.00028 | $0.00232 |
| Sonnet 5.5 | $0.00014 | $0.00116 |
| Haiku 4.5 | $0.00007 | $0.00058 |
Grade A, and why
vitest-guide 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.
How it starts
The opening of the file, as written. The whole thing — 37 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Vitest Testing Guidelines
For framework-independent test design: Arrange-Act-Assert, FIRST, and choosing/naming test doubles, see testing-guide; this guide covers only Vitest-specific mechanics.
Requirements
- Vitest ≥ 3, TypeScript ≥ 5.8
Essentials
- Type safety - Cast
res.json()to declared interfaces, see references/type-safety.md - HTTP testing - Assert the status the middleware actually sends, see references/http-testing.md
- Timestamp testing - Avoid flaky comparisons; verify existence or add delays, see references/timestamp-testing.md
- TypeScript config - Include test paths; verify project reference levels, see references/typescript-config.md
- Test organization - Mirror API structure under
test/with nested describe blocks, see references/test-organization.md
Gotchas
- Vitest transforms (
vite-node) differ from Jest:__dirname/__filenamework in CommonJS but not ESM tests without polyfills vi.spyOnreturns the spy;vi.fncreates a new mock: confusing them passes type checks but breaks call-tracking assertionsexpect.assertions(n)in async tests catches missed awaits, without it, a forgottenawaitlets the test pass spuriously- Watch mode caches module graphs; changing
vitest.config.tsrequires a full restart to pick up new transforms
Progressive disclosure
- Read references/type-safety.md - Load when calling
res.json()or test variables lose type information - Read references/http-testing.md - Load when asserting HTTP status codes or testing CORS OPTIONS requests
- Read references/timestamp-testing.md - Load when tests fail intermittently due to timing
- Read references/mock-patterns.md - Load when creating mocks or stubs for tests
- Read references/typescript-config.md - Load when test files aren't recognized by TypeScript or reference imports fail
- Read references/test-organization.md - Load when structuring test suites for large APIs
What ships with it
10 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.
- 1mo ago First seen · 37 lines · 71 tokens per session scan A 50fead3df268
vitest-guide is a skill published in the GitHub repository xonovex/platform (6 stars, last pushed 5d ago), licensed MIT. It adds 71 tokens to every session and 581 once invoked, about $0.0003 per session on Opus 5.5. 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 2026-09-08.
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