Book Image

Test-Driven iOS Development with Swift - Fourth Edition

By : Dr. Dominik Hauser
Book Image

Test-Driven iOS Development with Swift - Fourth Edition

By: Dr. Dominik Hauser

Overview of this book

Test-driven development (TDD) is a proven way to find software bugs earlier on in software development. Writing tests before you code improves the structure and maintainability of your apps, and so using TDD in combination with Swift 5.5's improved syntax leaves you with no excuse for writing bad code. Developers working with iOS will be able to put their knowledge to work with this practical guide to TDD in iOS. This book will help you grasp the fundamentals and show you how to run TDD with Xcode. You'll learn how to test network code, navigate between different parts of the app, run asynchronous tests, and much more. Using practical, real-world examples, you'll begin with an overview of the TDD workflow and get to grips with unit testing concepts and code cycles. You'll then develop an entire iOS app using TDD while exploring different strategies for writing tests for models, view controllers, and networking code. Additionally, you'll explore how to test the user interface and business logic of iOS apps and even write tests for the network layer of the sample app. By the end of this TDD book, you'll be able to implement TDD methodologies comfortably in your day-to-day development for building scalable and robust applications.
Table of Contents (17 chapters)
Section 1 –The Basics of Test-Driven iOS Development
Section 2 –The Data Model
Section 3 –Views and View Controllers
Section 4 –Networking and Navigation

Chapter 1: Your First Unit Tests

When the iPhone platform was first introduced, applications were small and focused only on one feature. It was easy to make money with an app that only did one thing (for example, a flashlight app that only showed a white screen). The code of these early apps only had a few hundred lines and could easily be tested by tapping the screen for a few minutes.

Since then, the App Store and the available apps have changed a lot. There are still small apps with a clear focus in the App Store, but it's much harder to make money from them. A common app has many features but still needs to be easy to use. There are companies with several developers working on one app full-time. These apps sometimes have a feature set that is normally found in desktop applications. It is very difficult and time-consuming to test all the features in such apps manually for every update.

One reason for this is that manual testing needs to be done through a user interface (UI), and it takes time to load the app to be tested. In addition to this, human beings are very slow compared to the capabilities of computers for tasks such as testing and verifying computer programs. Most of the time, a computer (or a smartphone) waits for the user's next input. If we could let a computer insert values, testing could be drastically accelerated. In fact, a computer can run several hundred tests within a few seconds. This is exactly what unit tests are all about.

A unit test is a piece of code that executes some other code and checks whether the result is what the developer expected. The word "unit" means that the test executes a small unit of code. Usually, that is one function of a class or some similar type of structure. How big the unit actually is depends on the feature to be tested and on the person who is writing the test.

Writing unit tests seems hard at first because for most developers, it's a new concept. This chapter is aimed at helping you get started with writing your first simple unit tests.

These are the main topics we will cover in the chapter:

  • Building your first automatic unit test
  • Assert functions in the XCTest framework
  • Understanding the difference from other kinds of tests