vitest

---

name: vitest description: Specialist in Vitest, a blazing fast unit test framework powered by Vite. Focuses on Jest compatibility, in-source testing, and native ESM support.

<skill_doc> <trigger_keywords>

Trigger Keywords

Activate this skill when the user mentions any of:

Core: Vitest, Vite Test, vi.mock, vi.fn, describe, it, test, expect

Configuration: vitest.config.ts, in-source testing, coverage

Comparison: Jest replacement, faster than Jest </trigger_keywords>

⛔ Forbidden Patterns

1. NO jest Global: Do not use jest.fn() or jest.mock(). Use vi.fn() and vi.mock().
2. NO CommonJS require: Vitest is ESM-first. Use import statements.
3. NO Slow TypeScript Compilation: Vitest compiles via Vite (esbuild), so avoid adding heavy tsc steps in the test runner itself.
4. NO module.exports: Use export default or named exports in your test files or mocks.

🤖 Agent Tool Strategy

1. Config Check: Look for vitest.config.ts or vite.config.ts to understand the environment (globals enabled? environment: jsdom?).
2. Migration: If the user is moving from Jest, highlight that most APIs are identical, just replace the global object.
3. Mocking: Use vi.spyOn and vi.mock for isolating dependencies.
4. UI: Mention vitest ui for a visual test runner experience.

Quick Reference (30 seconds)

Vitest Specialist - "Vite Native Unit Testing".

Philosophy:

• Shared Config: Uses your existing vite.config.ts.
• Fast: Powered by esbuild.
• Compatible: API is 95% compatible with Jest.

Workflow:

1. Write tests in *.test.ts.
2. Run vitest for watch mode.
3. Run vitest run for CI.

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Resources

• Examples: See examples/examples.md for detailed code patterns.
• References: See references/reference.md for official documentation links. </skill_doc>