Vitest

What it does

This skill provides access to Vitest, a testing framework designed as a drop-in replacement for Jest. It leverages Vite's transformation pipeline for fast test updates and offers features like smart watch mode, native support for ESM, TypeScript, and JSX, all without requiring complex configuration. Vitest is particularly useful for projects already using Vite due to its seamless integration with existing configurations, transformers, resolvers, and plugins.

When to use it

• Testing JavaScript or TypeScript codebases that utilize Vite as a build tool.
• Migrating from Jest to Vitest for faster test execution and improved developer experience.
• Developing projects requiring native ESM, TypeScript, or JSX support in tests.
• Running automated tests with parallel execution using multi-threaded workers.
• Generating code coverage reports using V8 or Istanbul providers.

Key capabilities

• Vite-native: Fast test updates leveraging Vite's transformation pipeline.
• Jest-compatible API: Easy migration from existing Jest test suites.
• Smart watch mode: Only reruns affected tests based on module dependencies.
• Native ESM, TypeScript, and JSX support: No extra configuration needed.
• Multi-threaded workers: Parallel test execution for faster results.
• Snapshot testing: Compare snapshots of component output over time.
• Mocking utilities: Mock functions, modules, timers, and dates.
• Coverage reporting: Generate code coverage reports using V8 or Istanbul.

Example prompts

• "Run all tests in the src directory."
• "Execute only the tests matching the pattern *.test.ts."
• "Generate a code coverage report for the project."
• "Run the test suite and display results with concurrency enabled."

Tips & gotchas

• This skill is based on Vitest 3.x, so ensure compatibility with your existing codebase.
• Vitest integrates seamlessly with Vite configurations; leverage existing vite.config.js or similar files for optimal setup.
• The skill supports various testing environments including node, jsdom, and happy-dom.