Building Testable Swiftdata Apps

A chapter from an upcoming iOS testing book covering how to write meaningful unit tests for SwiftData apps. The key argument is that developers should test their own business logic rather than verifying SwiftData's built-in insert/save/fetch operations. Topics include using in-memory stores for test isolation, identifying low-value tests, extracting logic into testable types like BudgetSummary, using helper factory functions to reduce test setup complexity, and leveraging the new ResultsObserver API (iOS 27) to test observable stores outside of SwiftUI views. Concrete code examples demonstrate testing duplicate name validation, computed budget totals, and aggregate summary calculations.