Jest Vitest

This is the skill you reach for when writing unit tests in JavaScript or TypeScript projects. It covers both Jest and Vitest with equal depth, focusing on the shared describe/it/expect API, mocking strategies with vi.fn and jest.fn, snapshot testing, and coverage analysis. The guidance is opinionated in the right ways: mock at boundaries not internals, test behavior not implementation, keep tests fast and in-memory. It includes practical examples of the Arrange-Act-Assert pattern, async testing with resolves/rejects, and module mocking setups. If you're testing React components with Testing Library or migrating a suite from Jest to Vitest, this gives you the patterns and anti-patterns you need.

Install to Claude Code

npx -y skills add absolutelyskilled/absolutelyskilled --skill jest-vitest --agent claude-code