Vitest

This is a prioritized collection of 44 Vitest testing rules organized into eight categories, from critical async patterns and test isolation down to lower priority concerns like test organization. What makes it useful is the explicit priority system: you know to fix async await issues and mock cleanup before worrying about snapshot formatting. It covers the tricky parts like vi.mock hoisting behavior, choosing between spyOn and mock, and performance tuning with pools and sharding. The quick reference table lets you scan by impact level, which beats scrolling through alphabetical lists when you're debugging flaky tests at 3pm. If you're migrating from Jest or trying to speed up your CI pipeline, the performance and mocking sections are worth reading first.