Vitest Test Runner Patterns

Quick Guide: Vitest runs tests through the same transform pipeline and config the app is built with, so aliases, plugins and TypeScript work without a second toolchain. describe/it/expect for structure, vi.fn() and vi.spyOn() for test doubles, vi.mock() for whole modules, and vi.useFakeTimers() for anything clock-driven. Vitest 4 is current stable (Vite 6+, Node 20+) and changed several mock defaults — vi.restoreAllMocks() no longer resets automocks, and poolOptions is gone.

Detailed Resources:

• examples/core.md — test structure and options, spies, module mocking, fake timers, assertions and snapshots
• examples/integration.md — setup files, lifecycle hooks, environments, and mocking at the transport boundary
• examples/anti-patterns.md — what not to write a test for
• reference.md — v3/v4 migration notes, config and mock API lookup