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.

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Table of Contents (17 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the example code files
Download the color images
Conventions used
Get in touch
Share Your Thoughts
1
Section 1 –The Basics of Test-Driven iOS Development
Section 1 –The Basics of Test-Driven iOS Development
Free Chapter
2
Chapter 1: Your First Unit Tests
Chapter 1: Your First Unit Tests
Technical requirements
Building your first automatic unit test
Assert functions in the XCTest framework
Understanding the difference from other kinds of tests
Summary
Exercises
3
Chapter 2: Understanding Test-Driven Development
Chapter 2: Understanding Test-Driven Development
The origin of TDD
The TDD workflow – red, green, refactor
The advantages of TDD
The disadvantages of TDD
What to test
Summary
4
Chapter 3: Test-Driven Development in Xcode
Chapter 3: Test-Driven Development in Xcode
Technical requirements
An example of TDD
Finding information about tests in Xcode
Running tests
Setting up and tearing down
Debugging tests
Summary
Exercises
5
Section 2 –The Data Model
Section 2 –The Data Model
6
Chapter 4: The App We Are Going to Build
Chapter 4: The App We Are Going to Build
Technical requirements
A list of to-do items
A view for the details of a to-do item
A view to add to-do items
The structure of the app
Getting started in Xcode
Summary
Exercises
7
Chapter 5: Building a Structure for ToDo Items
Chapter 5: Building a Structure for ToDo Items
Technical requirements
Implementing the ToDoItem struct
Implementing the Location struct
Summary
Exercises
8
Chapter 6: Testing, Loading, and Saving Data
Chapter 6: Testing, Loading, and Saving Data
Technical requirements
Publishing changes with Combine
Checking items
Storing and loading ToDoItems
Summary
Exercises
9
Section 3 –Views and View Controllers
Section 3 –Views and View Controllers
10
Chapter 7: Building a Table View Controller for the To-Do Items
Chapter 7: Building a Table View Controller for the To-Do Items
Technical requirements
Adding the table view for the to-do items
Testing the data source of a table view
Refactoring to a diffable data source
Presenting two sections
Implementing the delegate of a table view
Summary
Exercises
11
Chapter 8: Building a Simple Detail View
Chapter 8: Building a Simple Detail View
Technical requirements
Adding labels, a button, and a map
Filling in the data
Checking the to-do item
Summary
Exercises
12
Chapter 9: Test-Driven Input View in SwiftUI
Chapter 9: Test-Driven Input View in SwiftUI
Technical requirement
Adding the ViewInspector package
Using ViewInspector to test a simple view
Testing button actions with ViewInspector
Summary
Exercises
13
Section 4 –Networking and Navigation
Section 4 –Networking and Navigation
14
Chapter 10: Testing Networking Code
Chapter 10: Testing Networking Code
Mocking CLGeoCoder
Testing async/await code that communicates with URLSession
Handling errors
Summary
Exercises
15
Chapter 11: Easy Navigation with Coordinators
Chapter 11: Easy Navigation with Coordinators
Technical requirement
Testing the app's setup
Navigating to the details
Navigating to a modal view
Adding missing parts
Summary
Exercises
Why subscribe?
16
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Handling errors

To test the handling of errors in the URLSession call to the web service, we first need to enhance URLSessionProtocolMock. Follow these steps to test that an error in fetching data is passed down to the caller of the APIClient instance:

  1. Add the following property to URLSessionProtocolMock:
    // URLSessionProtocolMock.swift
var dataForDelegateError: Error?
  2. Next, add the following handling of the error to the start of data(for:delegate:):
    // URLSessionProtocolMock.swift
if let error = dataForDelegateError {
  throw error
}

If there is an error set to the dataForDelegateError property, we throw it before we do anything else in this method.

  1. Now, we are ready to add the test method to APIClientTests:
    // APIClientTests.swift
func test_toDoItems_whenError_shouldPassError() async
 throws {
  let urlSessionMock = URLSessionProtocolMock()
  let expected = NSError(domain: "", code: 1234)
  urlSessionMock.dataForDelegateError...
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