Testing Best Practices

A comprehensive testing reference that covers the fundamentals through 34 rules organized by priority, from critical test structure and isolation patterns down to performance optimizations. You'll want this when writing new tests, reviewing PRs, or setting up testing infrastructure. It's opinionated about the AAA pattern, test independence, and strategic mocking at boundaries rather than everywhere. The examples use TypeScript with Jest/Vitest, and it's honest about controversial topics like why 100% coverage shouldn't be your goal. The rule prefixes make it easy to scan for what matters most when you're in a hurry.