Название: Mockito Made Clear: Java Unit Testing with Mocks, Stubs, and Spies
Автор: Ken Kousen
Издательство: Pragmatic Bookshelf
Год: January 2023 (Version: P1.0)
Страниц: 131
Язык: английский
Формат: pdf, epub, mobi
Размер: 10.2 MB

Mockito is the most popular framework in the Java world for automating unit testing with dependencies. Learn the Mockito API and how and when to use stubs, mocks, and spies. On a deeper level, discover why the framework does what it does and how it can simplify unit testing in Java. Using Mockito, you'll be able to isolate the code you want to test from the behavior or state of external dependencies without coding details of the dependency. You'll gain insights into the Mockito API, save time when unit testing, and have confidence in your Java programs.

If you've only ever run a few JUnit tests or injected stubs into classes to return preset values, it's time to level up your Java toolbox. Dependencies on other classes and external resources can obscure issues and make bugs hard to detect. You need to test classes in isolation to truly pinpoint your problems. And while you could write dummy classes to replace dependencies yourself, Mockito automates the process and helps you fix your code faster.

Start with the Mockito API to generate fake classes for dependencies, configure how each should respond when their methods are called, and verify that the class under test interacts with dependencies the way you'd expect. Next, build unit tests with the Mockito framework and feel confident not just that methods are called, but that they are called the correct number of times and in the correct order. Along the way, follow clear test examples based on JUnit 5 to create stubs, mocks, and spies and find the source of any problems lurking in Java classes.

This book is about the Mockito testing framework, but it’s not an exhaustive reference. No books these days try to do that. For any library, the online documentation beats printed books every time because it keeps up with new versions of the software and can be adjusted to show new features and bug fixes. Where books become valuable is as a front end to the online docs, in that they help you understand what you’re getting into and what to expect when you get there. Books are curated content. They try to show you what’s important and why.

For Mockito, a book like this one is especially important, because the online documentation contains significant gaps. The docs were written by developers who understand tools like Mockito that generate mocks, stubs, and spies and who help you use them. That’s good, in that the docs focus on exactly how to make the framework do what you want. The downside is that you need to understand the problems that Mockito solves ahead of time, and unless you’ve already had experience with similar tools, those concepts are probably not obvious.

This book is intended to fill that gap. It’s about the concepts behind Mockito more than showing the details of how to use it. Those details are included, of course, for a set of representative examples, but the goal is understanding rather than the specific details of the syntax. The online docs are good for syntax (the classes and methods in the API) and, to a lesser extent, semantics (how to use the tool to do what you want), but they don’t explain why Mockito is useful in the first place or how it can make your job easier.

Save time, write better code, and have more confidence in your Java programs with Mockito.

What You Need:

In this book, we use Mockito 4, the latest version of the Mockito framework, but the concepts and the code works on versions 2 and 3. The tests are based on JUnit 5 (known as Jupiter). There are some differences in JUnit 4, but none of those affect Mockito directly. The underlying Java version is 11, but the provided tests in the GitHub repository will work successfully for any version of Java above that (including the current Long Term Support version, 17).

Table of Contents:
Preface
Chapter 1: Build a Testing Foundation
Chapter 2: Work with the Mockito API
Chapter 3: Use Built-in and Custom Matchers
Chapter 4: Solve Problems with Mockito
Chapter 5: Use Mockito in Special Cases
Appendix 1: Running Mockito Tests