Unit Testing Skill (Vitest)

Write fast, isolated unit tests with Vitest for TypeScript logic — utilities, Zod schemas, hooks, and Server Actions (with dependencies mocked). Unit tests do NOT render components in a browser (use the storybook-testing skill for that).

This file holds the rules. Code lives in the references:

• references/examples.md — seven worked examples: pure utility, Zod schema, Server Action with mocked DB, transform function, parameterized (it.each), async error handling, hooks.
• references/patterns.md — AAA, test isolation, mock boundaries, the vi.mock vs vi.fn vs vi.spyOn decision table, coverage targets, and anti-patterns.
• references/mocking.md — the full mocking catalogue (factories, hoisting, partial/dynamic mocks, async, DB/auth/time/env recipes). Read before writing non-trivial mocks.

Global Test Utilities

This project enables global test utilities — do not import them: