Test-Driven Development in Swift

Leverage Swift to practice effective and efficient test-driven development (TDD) methodology. Software testing and TDD are evergreen programming concepts—yet Swift developers haven’t widely adopted them. What’s needed is a clear roadmap to learn and adopt TDD in the Swift world. Over the past years, Apple has invested in XCTest and Xcode’s testing infrastructure, making testing a new top priority in their ecosystem. Open-source libraries such as Quick and Nimble have also reached maturity. The tools are there. This book will show you how to wield them. 

TDD has much more to offer than catching bugs. With this book, you’ll learn a philosophy for building software. TDD enables engineers to solve problems incrementally, writing only as much code as necessary. By decomposing big problems into small steps, you can move along at a fast pace, always making visible progress. 

Participate in the test-driven development journey by building a real iOS application and incorporating new concepts through each chapter. The book’s concepts will emerge as you figure out ways to use tests to drive the solutions to the problems of each chapter. Through the TDD of a single application, you’ll be introduced to all the staples and advanced concepts of the craft, understand the trade offs each technique offers, and review an iterative process of software development. 

Test-Driven Development in Swift provides the path for a highly efficient way to make amazing apps.

What You’ll Learn

• Write tests that are easy to maintain
• Look after an ever-growing test suite
• Build a testing vocabulary that can be applied outside the Swift world
• See how Swift programming enhances the TDD flow seen in dynamic languages 
• Discover how compiler errors can provide the same helpful guidance as failing tests do

Who This Book Is For

Mid-level developers keen to write higher quality code and improve their workflows. Also, developers that have already been writing tests but feel they are not getting the most out of them. 

Table of Contents

Chapter 1: Why Test-Driven Development?

Chapter 2: XCTest Introduction

Chapter 3: Getting Started with Test-Driven Development

Chapter 4: Test-Driven Development in the Real World

Chapter 5: Changing Tests with Fixtures

Chapter 6: Testing Static SwiftUI Views

Chapter 7: Testing Dynamic SwiftUI Views

Chapter 8: Testing Code Based on Indirect Inputs

Chapter 9: Testing JSON Decoding

Chapter 10: Testing Network Code

Chapter 11: Injecting Dependencies with @EnvironmentObject

Chapter 12: Testing Side Effects

Chapter 13: Testing a Conditional View Presentation

Chapter 14: Fixing Bugs and Changing Existing Code with TDD

Chapter 15: Keeping Tests Isolated with Fakes and Clear with Dummies

Chapter 16: Conclusion Cheatsheet

Appendix A: Where to Go from Here

Append ix B: Testing with Quick and Nimble

Appendix C: TDD with UIKit

About the Author

Gio Lodi spent the past decade writing tests. He began with full-stack web development before moving into iOS programming and, more recently, into mobile infrastructure engineering. Ruby on Rails introduced him to the TDD world, and he fell in love with the fast-paced feedback loop. Any big problem could be decomposed in smaller and smaller parts until it got to an achievable size. Due to the lack of tools he first encountered moving into the Apple ecosystem, Gio researched and experimented with testing strategies and tools document in an ongoing project that catalogued on his blog and in talks and workshops at various industry conferences.