Swift Testing

This walks you through Swift Testing, Apple's macro-based replacement for XCTest. It covers the #expect/#require distinction (most checks should use #expect, not #require), async testing without the Task wrapper nonsense, and parameterized tests with zip to avoid accidental Cartesian products. The migration table from XCTest assertions is handy if you're converting existing tests. Biggest gotcha: tests run in parallel by default, so you'll need .serialized for anything touching shared state. Good reference if you're tired of XCTest's verbosity or finally moving a real codebase to the new framework.