Vitest Test Runner Patterns

Quick Guide: Vitest is a fast, Vite-native test runner. Use describe/it/expect for test structure, vi.fn() for mocks, vi.mock() for module mocking, vi.spyOn() for spying. Co-locate tests with code. Use network-level API mocking over module-level mocks. Vitest v4 is current stable (requires Vite 6+, Node 20+).

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CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST co-locate tests with code in feature-based structure - NOT in separate test directories)

(You MUST use network-level API mocking - NOT module-level mocks where possible)

(You MUST use named constants for test data - no magic strings or numbers in test files)

(You MUST use vi.fn() for mocks and vi.spyOn() for spying - NEVER manually replace functions)