Book Image

Test-Driven Java Development

Book Image

Test-Driven Java Development

Overview of this book

Table of Contents (17 chapters)
Test-Driven Java Development
About the Authors
About the Reviewers
Refactoring Legacy Code – Making it Young Again


Test-driven development has been around for a while and many people have still not adopted it. The reason behind this is that TDD is difficult to master. Even though the theory is very easy to grasp, it takes a lot of practice to become really proficient with it.

Authors of this book have been practicing TDD for years and will try to pass on their experience to you. They are developers and believe that the best way to learn some coding practice is through code and constant practice. This book follows the same philosophy. We'll explain all the TDD concepts through exercises. This will be a journey through the TDD best practices applied to Java development. At the end of it, you will earn a TDD black belt and have one more tool in your software craftsmanship tool belt.

What this book covers

Chapter 1, Why Should I Care for Test-driven Development?, spells out our goal of becoming a Java developer with a TDD black belt. In order to know where we're going, we'll have to discuss and find answers to some questions that will define our voyage.

Chapter 2, Tools, Frameworks, and Environments, will compare and set up all the tools, frameworks and environments that will be used throughout this book. Each of them will be accompanied with code that demonstrates their strengths and weaknesses.

Chapter 3, Red-Green-Refactor – from Failure through Success until Perfection, will help us develop a Tic-Tac-Toe game using the red-green-refactor technique, which is the pillar of TDD. We'll write a test and see it fail; we'll write a code that implements that test, run all the tests and see them succeed, and finally, we'll refactor the code and try to make it better.

Chapter 4, Unit Testing – Focusing on What You Do and Not on What Has Been Done, shows that to demonstrate the power of TDD applied to unit testing, we'll need to develop a Remote Controlled Ship. We'll learn what unit testing really is, how it differs from functional and integration tests, and how it can be combined with test-driven development.

Chapter 5, Design – If It's Not Testable, It's Not Designed Well, will help us develop a Connect4 game without any tests and try to write tests at the end. This will give us insights into the difficulties we are facing when applications are not developed in a way that they can be tested easily.

Chapter 6, Mocking – Removing External Dependencies, shows how TDD is about speed. We want to quickly demonstrate some idea/concept. We'll continue developing our Tic-Tac-Toe game by adding MongoDB as our data storage. None of our tests will actually use MongoDB since all communications to it will be mocked.

Chapter 7, BDD – Working Together with the Whole Team, discusses developing a Book Store application by using the BDD approach. We'll define the acceptance criteria in the BDD format, carry out the implementation of each feature separately, confirm that it is working correctly by running BDD scenarios, and if required, refactor the code to accomplish the desired level of quality.

Chapter 8, Refactoring Legacy Code – Making it Young Again, will help us refactor an existing application. The process will start with creation of test coverage for the existing code and from there on we'll be able to start refactoring until both the tests and the code meet our expectations.

Chapter 9, Feature Toggles – Deploying Partially Done Features to Production, will show us how to develop a Fibonacci calculator and use feature toggles to hide functionalities that are not fully finished or that, for business reasons, should not yet be available to our users.

Chapter 10, Putting It All Together, will walk you through all the TDD best practices in detail and refresh the knowledge and experience you gained throughout this book.

What you need for this book

The exercises in this book require readers to have a 64 bit computer. Installation instructions for all required software is provided throughout the book.

Who this book is for

If you're an experienced Java developer and want to implement more effective methods of programming systems and applications, then this book is for you.


In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.

Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "We can include other contexts through the use of the include directive."

A block of code is set as follows:

public class Friendships {
    private final Map<String, List<String>> friendships = new HashMap<>();

    public void makeFriends(String person1, String person2) {
        addFriend(person1, person2);
        addFriend(person2, person1);

Any command-line input or output is written as follows:

$> vagrant plugin install vagrant-cachier
$> git clone t

New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Once we type our search query, we should find and click the Go button."


Warnings or important notes appear in a box like this.


Tips and tricks appear like this.

Reader feedback

Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of.

To send us general feedback, simply e-mail , and mention the book's title in the subject of your message.

If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide at

Customer support

Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.


Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you could report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting, selecting your book, clicking on the Errata Submission Form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded to our website or added to any list of existing errata under the Errata section of that title.

To view the previously submitted errata, go to and enter the name of the book in the search field. The required information will appear under the Errata section.


Piracy of copyrighted material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works in any form on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy.

Please contact us at with a link to the suspected pirated material.

We appreciate your help in protecting our authors and our ability to bring you valuable content.


If you have a problem with any aspect of this book, you can contact us at , and we will do our best to address the problem.