vitest-skill

Import describe, it, expect, and beforeEach from 'vitest', then structure tests around the module under test. Vitest is TypeScript-first, so typed test files run natively without extra transpilation setup.

Call vi.mock('./module', () => ({ ... })) at the top of the test file to replace module exports with mock implementations. Use vi.fn().mockResolvedValue() for async functions and vi.spyOn for partial spying on existing objects.

Vitest uses the vi namespace instead of jest: vi.fn() replaces jest.fn() and vi.mock() replaces jest.mock(). The assertion API remains Jest-compatible, so expect statements and matchers work the same way.

Yes, Vitest works with @testing-library/react when the environment is set to 'jsdom' in vitest.config.ts. Render components with render() and assert on output using screen queries like getByText.

Run npx vitest --coverage to generate coverage using the v8 provider configured in vitest.config.ts. Reporters such as text and html can be specified under the coverage.reporter option.

In-source testing via import.meta.vitest co-locates tests in production files, which can bloat bundles if not stripped at build time. Use it for small utility modules, but prefer separate test files for larger suites.