Testing Fundamentals
DanielPodolsky/ownyourcode
Guides test strategy for unit, integration, and E2E testing.
Vitest API and config reference (Jest-compatible) — mocking with vi., spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering.
Install Vitest
$ npx skills add supabase/supabase --skill vitest -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install supabase/supabase vitest --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/supabase/supabase.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/vitest .claude/skills/vitest && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "vitest" agent skill from https://github.com/supabase/supabase/tree/master/.agents/skills/vitest into .claude/skills/vitest/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/supabase/supabase/tree/master/.agents/skills/vitestType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add supabase/supabase --skill vitest -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install supabase/supabase vitest --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/supabase/supabase.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/vitest .agents/skills/vitest && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "vitest" agent skill from https://github.com/supabase/supabase/tree/master/.agents/skills/vitest into .agents/skills/vitest/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add supabase/supabase --skill vitest -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install supabase/supabase vitest --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/supabase/supabase.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/vitest .cursor/skills/vitest && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "vitest" agent skill from https://github.com/supabase/supabase/tree/master/.agents/skills/vitest into .cursor/skills/vitest/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/supabase/supabase.git --path .agents/skills/vitest--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add supabase/supabase --skill vitest -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install supabase/supabase vitest --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/supabase/supabase.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/vitest .gemini/skills/vitest && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "vitest" agent skill from https://github.com/supabase/supabase/tree/master/.agents/skills/vitest into .gemini/skills/vitest/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install supabase/supabase vitestInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add supabase/supabase --skill vitest -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/supabase/supabase.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/vitest .github/skills/vitest && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "vitest" agent skill from https://github.com/supabase/supabase/tree/master/.agents/skills/vitest into .github/skills/vitest/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add supabase/supabase --skill vitest -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install supabase/supabase vitest --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/supabase/supabase.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/vitest .opencode/skills/vitest && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "vitest" agent skill from https://github.com/supabase/supabase/tree/master/.agents/skills/vitest into .opencode/skills/vitest/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "vitest", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
vitest- GitHub stars
- 111k
- Used in
- 12 other repos
- Token cost
- ~1.1k tokens
- SKILL.md length
- 261 words
- Files
- 18 (incl. references)
- Skills in repo
- 22
- Repo updated
- First seen
- Licence
- Apache-2.0
At a glance
Vitest API and config reference (Jest-compatible) — mocking with vi., spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering.
- Vitest API and configuration questions anywhere in the monorepo
- SKILL.md covers Core, Features and Advanced
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- For Studio-specific test strategy and component-test setup
What it does
Vitest is an agent skill from supabase/supabase, published by the product's own GitHub organization. Vitest API and config reference (Jest-compatible) — mocking with vi., spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering. Use for Vitest API and configuration questions anywhere in the monorepo; for Studio-specific test strategy and component-test setup, start with studio-testing and studio-mock-api-tests.
Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 18 other files, including reference files (for example `GENERATION.md`, `references/advanced-environments.md` and `references/advanced-projects.md`).
It sits in Testing & QA, covering Unit testing. It works with Vitest, Jest and Vite. The repository describes itself as: The Postgres development platform. Supabase gives you a dedicated Postgres database to build your web, mobile, and AI applications. The licence is Apache-2.0.
When your agent uses it
- Vitest API and configuration questions anywhere in the monorepo
- For Studio-specific test strategy and component-test setup
- Start with studio-testing and studio-mock-api-tests
Example prompts
- “/vitest”
What it can do on your machine
Read from SKILL.md and the folder at commit 26c838a. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Vitest loads about 1.1k tokens when it runs, and up to ~18k if it reads all its reference files. Until then it costs about 87 tokens; SKILL.md has 261 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from supabase/supabase at commit 26c838a, republished under its Apache-2.0 licence (© supabase). 261 words, ~1,090 tokens.
Download SKILL.mdSave it as
.claude/skills/vitest/SKILL.md (or your agent's skills folder). This skill also uses 17 other files; get the full folder from GitHub.- name
- vitest
- description
- Vitest API and config reference (Jest-compatible) — mocking with vi.*, spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering. Use for Vitest API and configuration questions anywhere in the monorepo; for Studio-specific test strategy and component-test setup, start with studio-testing and studio-mock-api-tests.
- metadata.author
- Anthony Fu
- metadata.version
- 2026.1.28
- metadata.source
- Generated from https://github.com/vitest-dev/vitest, scripts located at https://github.com/antfu/skills
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 |
Advanced
| Topic | Description | Reference |
|---|---|---|
| Vi Utilities | vi helper: mock, spyOn, fake timers, hoisted, waitFor | advanced-vi |
| Environments | Test environments: node, jsdom, happy-dom, custom | advanced-environments |
| Type Testing | Type-level testing with expectTypeOf and assertType | advanced-type-testing |
| Projects | Multi-project workspaces, different configs per project | advanced-projects |
© supabase, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 17 other files (references) in .agents/skills/vitest of supabase/supabase.
- SKILL.md
- GENERATION.md
- references/advanced-environments.md
- references/advanced-projects.md
- references/advanced-type-testing.md
- references/advanced-vi.md
- references/core-cli.md
- references/core-config.md
- references/core-describe.md
- references/core-expect.md
- references/core-hooks.md
- references/core-test-api.md
- references/features-concurrency.md
- references/features-context.md
- references/features-coverage.md
- references/features-filtering.md
- references/features-mocking.md
- references/features-snapshots.md
Open the folder on GitHubat commit 26c838a
Used in 12 other repositories
We found 12 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 12 other GitHub owners. This page covers the copy in supabase/supabase, which our catalogue first saw on October 8, 2026.
- JetBrains/skillsvitest
- graz-sh/graz.agents/skills/vitest
- victorgarciaesgi/regle.cursor/skills/vitest
- ever-works/ever-works.agents/skills/vitest
- bskimball/tanstack-hono.agents/skills/vitest
- pedronauck/skillsskills/curated/vitest
- anolilab/lunora.agents/skills/vitest
- aiskillstore/marketplaceskills/antfu/vitest
- NeverSight/learn-skills.devdata/skills-md/0froq/skills/vitest
- antfu/skillsskills/vitest
- LeoYeAI/openclaw-master-skillsskills/vitest
- compozy/compozy.agents/skills/vitest
Compare with similar skills
Vitest next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Vitest this skillsupabase/supabase | 111k | 12 repos | ~1.1k | Automated safety check: Pass | Apache-2.0 | |
| Testing FundamentalsDanielPodolsky/ownyourcode | 290 | 1 repos | ~1.5k | Automated safety check: Pass | MIT | |
| Vitest Skillsickn33/agentic-awesome-skills | 47k | 1 repos | ~1.2k | Automated safety check: Pass | MIT | |
| Vitestjezweb/claude-skills | 1.1k | — | ~3k | Automated safety check: Pass | MIT | |
| Tech Trend Watchmizchi/skills | 356 | — | ~1.8k | Automated safety check: Pass | None | |
| Test GuardamElnagdy/guard-skills | 1.3k | 2 repos | ~2.1k | Automated safety check: Pass | MIT |
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Related
Categories
Questions about Vitest
What does Vitest do?
Vitest API and config reference (Jest-compatible) — mocking with vi., spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering. Vitest is an agent skill from supabase/supabase, published by the product's own GitHub organization., spies, fake timers, coverage configuration, fixtures, snapshots, and test filtering.
When should I use Vitest?
Vitest fits situations like: vitest API and configuration questions anywhere in the monorepo; for Studio-specific test strategy and component-test setup; start with studio-testing and studio-mock-api-tests.
How do I install Vitest in Claude Code?
Run `npx skills add supabase/supabase --skill vitest -a claude-code`. Or copy the skill folder (.agents/skills/vitest in supabase/supabase) into .claude/skills/vitest in your project. Claude Code loads it when a task matches its description.
How do I install Vitest in Codex?
Run `npx skills add supabase/supabase --skill vitest -a codex`. Or copy the skill folder (.agents/skills/vitest in supabase/supabase) into .agents/skills/vitest in your project. Codex loads it when a task matches its description.
Can I use Vitest in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add supabase/supabase --skill vitest -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/vitest, .gemini/skills/vitest, .github/skills/vitest and .opencode/skills/vitest in your project.
What does Vitest need to run?
SKILL.md names no scripts, command-line tools or credentials: Vitest is instructions for the agent only.
Does Vitest access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Vitest safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Vitest use?
Vitest is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Vitest use?
About 1.1k tokens (SKILL.md is roughly 4.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 17k tokens, read only when the agent opens those files.
What are the alternatives to Vitest?
Skills that share tags, products or a category with Vitest: Testing Fundamentals (DanielPodolsky/ownyourcode, 290 stars), Vitest Skill (sickn33/agentic-awesome-skills, 47k stars), Vitest (jezweb/claude-skills, 1.1k stars) and Tech Trend Watch (mizchi/skills, 356 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Vitest?
supabase (a GitHub organization, an official publisher) maintains it in supabase/supabase, which has 111,222 GitHub stars. The repository holds 22 skills in this directory. The repository was last updated on October 8, 2026.
Source: supabase/supabase on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.