Agent skill · software engineering · onmax
vitest
Vitest fast unit testing framework powered by Vite with Jest-compatible API. Use when writing tests, mocking, configuring coverage, or working with test filtering and fixtures.
Why this skill is useful
Provides specific configuration patterns and testing methodologies for Vite projects that the AI wouldn't reliably generate on its own.
What it needs
Requires vitest installed locally. About 2k tokens when loaded. Last updated 2026-07-27. 697 stars on the source repository.
What this skill does
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 5.x (beta), generated at 2026-06-22. 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 Te …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills onmax/vitest