Book Image

SwiftUI Cookbook

By : Giordano Scalzo, Edgar Nzokwe
Book Image

SwiftUI Cookbook

By: Giordano Scalzo, Edgar Nzokwe

Overview of this book

SwiftUI is an innovative and simple way to build beautiful user interfaces (UIs) for all Apple platforms, right from iOS and macOS through to watchOS and tvOS, using the Swift programming language. In this recipe-based book, you’ll work with SwiftUI and explore a range of essential techniques and concepts that will help you through the development process. The recipes cover the foundations of SwiftUI as well as the new SwiftUI 2.0 features introduced in iOS 14. Other recipes will help you to make some of the new SwiftUI 2.0 components backward-compatible with iOS 13, such as the Map View or the Sign in with Apple View. The cookbook begins by explaining how to use basic SwiftUI components. Then, you’ll learn the core concepts of UI development such as Views, Controls, Lists, and ScrollViews using practical implementation in Swift. By learning drawings, built-in shapes, and adding animations and transitions, you’ll discover how to add useful features to the SwiftUI. When you’re ready, you’ll understand how to integrate SwiftUI with exciting new components in the Apple development ecosystem, such as Combine for managing events and Core Data for managing app data. Finally, you’ll write iOS, macOS, and watchOS apps while sharing the same SwiftUI codebase. By the end of this SwiftUI book, you'll have discovered a range of simple, direct solutions to common problems found in building SwiftUI apps.
Table of Contents (15 chapters)

Snapshot testing SwiftUI views

While snapshot testing is more common in other technologies, for example, JavaScript and the Jest testing library, (see https://jestjs.io/docs/en/snapshot-testing.html), in the iOS world it is not so common.

Snapshot testing is another name for characterization testing. Here's the definition by Michael Feathers, the guru of improving legacy code: https://michaelfeathers.silvrback.com/characterization-testing. In the SwiftUI implementation, we are taking a snapshot of the current component we want to preserve, and we run a test against that component so that if in the future someone mistakenly changes its appearance, the test will fail.In the case of iOS, usually a component we want to preserve is UIViewController or a UIView.

Depending on the library we are going to use, we can take the snapshot in different ways: as a textual description or an actual screenshot. For this recipe, we'll use the Swift Snapshot Testing library that you can...