vitest-skill

Q: How do I install vitest-skill?

Run npx skills add https://github.com/lambdatest/agent-skills --skill vitest-skill in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/vitest-skill/ (personal) or .claude/skills/vitest-skill/ (project).

by lambdatestTesting & QA

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".

Installs: 452
Last 24h: —
Trending rank: —
Security: Not audited

Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/lambdatest/agent-skills --skill vitest-skill

01
Install
Run the command in your project. The CLI asks which agents to install for.
02
Describe the task
Ask your agent for something this skill covers. It loads vitest-skill automatically when relevant.
03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Vitest Testing Skill

Core Patterns

Basic Test

import { describe, it, expect, vi, beforeEach } from 'vitest';
import { Calculator } from './calculator';

describe('Calculator', () => {
  let calc: Calculator;
  beforeEach(() => { calc = new Calculator(); });

  it('adds two numbers', () => {
    expect(calc.add(2, 3)).toBe(5);
  });

  it('throws on divide by zero', () => {
    expect(() => calc.divide(10, 0)).toThrow();
  });
});

Mocking (vi instead of jest)

import { vi } from 'vitest';

// Mock module
vi.mock('./database', () => ({
  getUser: vi.fn().mockResolvedValue({ name: 'Alice' }),
  saveUser: vi.fn().mockResolvedValue(true),
}));

// Mock function
const mockFn = vi.fn();
mockFn.mockReturnValue(42);
mockFn.mockResolvedValue({ data: 'test' });

// Spy
const spy = vi.spyOn(console, 'log').mockImplementation(() => {});
expect(spy).toHaveBeenCalledWith('message');
spy.mockRestore();

// Timers
vi.useFakeTimers();
vi.advanceTimersByTime(1000);
vi.runAllTimers();
vi.useRealTimers();

In-Source Testing

// src/math.ts — tests alongside code!
export function add(a: number, b: number) { return a + b; }
export function multiply(a: number, b: number) { return a * b; }

if (import.meta.vitest) {
  const { it, expect } = import.meta.vitest;
  it('adds', () => { expect(add(2, 3)).toBe(5); });
  it('multiplies', () => { expect(multiply(3, 4)).toBe(12); });
}

Snapshot Testing

it('serializes user', () => {
  expect(serializeUser(user)).toMatchSnapshot();
});

it('inline snapshot', () => {
  expect(serializeUser(user)).toMatchInlineSnapshot(`
    { "name": "Alice", "email": "alice@test.com" }
  `);
});

React Component Testing

import { render, screen } from '@testing-library/react';
import { describe, it, expect } from 'vitest';
import Button from './Button';

describe('Button', () => {
  it('renders with label', () => {
    render(<Button label="Click me" />);
    expect(screen.getByText('Click me')).toBeDefined();
  });
});

Anti-Patterns

Bad	Good	Why
`jest.fn()`	`vi.fn()`	Vitest uses `vi`
`jest.mock()`	`vi.mock()`	Different namespace
No type safety	TypeScript + strict	Vitest is TS-first

Quick Reference

Task	Command
Run once	`npx vitest run`
Watch	`npx vitest` (default)
UI	`npx vitest --ui`
Coverage	`npx vitest --coverage`
Specific file	`npx vitest run src/math.test.ts`
Filter	`npx vitest run -t "adds"`

vitest.config.ts

import { defineConfig } from 'vitest/config';
export default defineConfig({
  test: {
    globals: true,
    environment: 'jsdom',
    coverage: { provider: 'v8', reporter: ['text', 'html'] },
    include: ['src/**/*.{test,spec}.{js,ts,tsx}'],
    includeSource: ['src/**/*.{js,ts}'],
  },
});

Deep Patterns → `reference/playbook.md`

§	Section	Lines
1	Production Configuration	Config, workspace, setup file
2	Mocking Patterns	vi.mock, spies, timers, fetch
3	React Testing Library	Components, hooks, providers
4	Snapshot & Inline Snapshots	File, inline, serializers
5	Table-Driven Tests	test.each, describe.each
6	In-Source Testing	Co-located tests in source
7	API / Integration Testing	Server tests with fetch
8	CI/CD Integration	GitHub Actions, scripts
9	Debugging Quick-Reference	10 common problems
10	Best Practices Checklist	13 items

FAQ

What does the vitest-skill skill do?

How do I install vitest-skill?

Run npx skills add https://github.com/lambdatest/agent-skills --skill vitest-skill in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/vitest-skill/ (personal) or .claude/skills/vitest-skill/ (project).

Which AI agents can use vitest-skill?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is vitest-skill safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains vitest-skill?

It is published by lambdatest in lambdatest/agent-skills. It has 452 recorded installs.

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vitest-skill

Install

Install

Describe the task

Review the result

SKILL.md

Vitest Testing Skill

Core Patterns

Basic Test

Mocking (vi instead of jest)

In-Source Testing

Snapshot Testing

React Component Testing

Anti-Patterns

Quick Reference

vitest.config.ts

Deep Patterns → reference/playbook.md

FAQ

More from lambdatest/agent-skills

Popular testing & qa skills

Deep Patterns → `reference/playbook.md`