Testing with JUnit

Frank Appel

• Verlag: Packt Publishing
• Jahr: 2015
• ISBN:
  9781782166603
• Auflage: 1
• Thema: Computer Science
• Thema: Application Development

Master high quality software development driven by unit tests

About This Book

• Design and implement robust system components by means of the de facto unit testing standard in Java
• Reduce defect rate and maintenance effort, plus simultaneously increase code quality and development pace
• Follow a step-by-step tutorial imparting the essential techniques based on real-world scenarios and code walkthroughs

Who This Book Is For

No matter what your specific background as a Java developer, whether you're simply interested in building up a safety net to reduce regressions of your desktop application or in improving your server-side reliability based on robust and reusable components, unit testing is the way to go. This book provides you with a comprehensive but concise entrance advancing your knowledge step-wise to a professional level.

What You Will Learn

• Organize your test infrastructure and resources reasonably
• Understand and write well structured tests
• Decompose your requirements into small and independently testable units
• Increase your testing efficiency with on-the-fly generated stand-in components and deal with the particularities of exceptional flow
• Employ runners to adjust to specific test demands
• Use rules to increase testing safety and reduce boilerplate
• Use third party supplements to improve the expressiveness of your verification statements

In Detail

JUnit has matured to become the most important tool when it comes to automated developer tests in Java. Supported by all IDEs and build systems, it empowers programmers to deliver software features reliably and efficiently. However, writing good unit tests is a skill that needs to be learned; otherwise it's all too easy to end up in gridlocked development due to messed up production and testing code. Acquiring the best practices for unit testing will help you to prevent such problems and lead your projects to success with respect to quality and costs.

This book explains JUnit concepts and best practices applied to the test first approach, a foundation for high quality Java components delivered in time and budget.

From the beginning you'll be guided continuously through a practically relevant example and pick up background knowledge and development techniques step by step. Starting with the basics of tests organization you'll soon comprehend the necessity of well structured tests and delve into the relationship of requirement decomposition and the many-faceted world of test double usage. In conjunction with third-party tools you'll be trained in writing your tests efficiently, adapt your test case environment to particular demands and increase the expressiveness of your verification statements. Finally, you'll experience continuous integration as the perfect complement to support short feedback cycles and quality related reports for your whole team.

The tutorial gives a profound entry point in the essentials of unit testing with JUnit and prepares you for test-related daily work challenges.

Style and approach

This is an intelligible tutorial based on an ongoing and non-trivial development example. Profound introductions of concepts and techniques are provided stepwise as the programming challenges evolve. This allows you to reproduce and practice the individual skills thoroughly.

Testing with JUnit

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Table of Contents

Testing with JUnit

Credits

About the Author

About the Reviewers

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Downloading the color images of this book

Errata

Piracy

Questions

1. Getting Started

Why you should busy yourself with unit tests

Reducing the defect rate

Improving the code quality

Increasing the development pace

Enhancing the specification density

Boosting confidence and courage

Setting the table

Choosing the ingredients

Organizing your code

Serving the starter

Introducing the example app

Understanding the nature of a unit test

Writing the first test

Evaluating test results

Writing tests first

Summary

2. Writing Well-structured Tests

The four phases of a unit test

Using a common test structure

Setting up the fixture

What goes up must come down

Verification

Choosing the next functionality to test

Start with the happy path

Conclude with corner cases

After the war

Getting the test names right

Test prefix

Behavior-expressing patterns

Reducing names to the essentials

Summary

3. Developing Independently Testable Units

Decomposing requirements

Separating concerns

Component dependencies

Understanding isolation

Delegating responsibilities to DOCs

Indirect input and output

Unit isolation with test doubles

Working with test doubles

Placeholder dummies

Fake it till you make it

Providing indirect input with stubs

Recording interactions with spies

Verifying behavior with mocks

Increasing efficiency with mock frameworks

The promised land?

Basic stubbing

Indirect output verification

Using test helpers

Motivation

The test helper class

The test helper object

Summary

4. Testing Exceptional Flow

Testing patterns

Using the fail statement

Annotated expectations

Verification with the ExpectedException rule

Capturing exceptions with closures

Treating collaborators

Fail fast

The stubbing of exceptional behavior

Summary

5. Using Runners for Particular Testing Purposes

Understanding the architecture

What are runners good for?

Looking at the big picture

Writing your own extension

Using custom runners

Furnishing a suite with test cases

Structuring suites into categories

Populating suites automatically

How about creating test doubles with annotations?

Writing dataset tests

Using parameterized tests

Reducing glue code with JUnitParams

Increasing the expressiveness of test descriptions with Burst

Summary

6. Reducing Boilerplate with JUnit Rules

Understanding rules

What are JUnit rules?

Writing your own rule

Configuring the fixture with annotations

Working with advanced concepts

Using ClassRules

The ordering of rule execution

Employing custom solutions

Working with system settings

Ignoring tests conditionally

Summary

7. Improving Readability with Custom Assertions

Working with the JUnit built-in assert approach

Understanding the basics

Reviewing the file session storage

Verifying the storage behavior

Improving readability with assertion helpers

Creating flexible expressions of intent with Hamcrest

Using matcher expressions

Writing custom matchers

Writing fluently readable assertions with AssertJ

Employing assertion chains

Creating your own asserts

Summary

8. Running Tests Automatically within a CI Build

Wrapping up the sample application

Refining the architecture

Separating concerns into modules

Setting up an automated CI build

What is continuous integration?

Principles and practices

Creating your own build

Integrating code coverage reports

Enlarging on code coverage

Automating reporting

Summary

A. References

Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

Index

Testing with JUnit

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: August 2015

Production reference: 1240815

Published by Packt Publishing Ltd.

Livery Place

35 Livery Street

Birmingham B3 2PB, UK.

ISBN 978-1-78216-660-3

www.packtpub.com

Credits

Author

Frank Appel

Reviewers

Stefan Birkner

Jose Muanis Castro

John Piasetzki

Acquisition Editor

Sonali Vernekar

Content Development Editor

Merwyn D'souza

Technical Editor

Humera Shaikh

Copy Editors

Sarang Chari

Sonia Mathur

Project Coordinator

Nikhil Nair

Proofreader

Safis Editing

Indexer

Monica Ajmera Mehta

Graphics

Jason Monteiro

Production Coordinator

Nilesh R. Mohite

Cover Work

Nilesh R. Mohite

About the Author

Frank Appel is a stalwart of agile methods and test-driven development in particular. He has over 2 decades of experience as a freelancer and understands software development as a type of craftsmanship. Having adopted the test first approach over a decade ago, he applies unit testing to all kinds of Java-based systems and arbitrary team constellations. He serves as a mentor, provides training, and blogs about these topics at codeaffine.com.

I'd like to thank the reviewers, John Piasetzki, Stefan Birkner, and Jose Muanis Castro, and the editors, Sonali Vernekar, Merwyn D'souza, and Humera Shaikh, who spent time and effort to point out my errors, omissions, and sometimes unintelligible writing. In particular, I would like to thank my friend Holger Staudacher, who helped in the reviewing process of the book.

Thanks to all of you for your valuable input and support!

About the Reviewers

Stefan Birkner has a passion for software development. He has a strong preference for beautiful code, tests, and deployment automation. Stefan is a contributor to JUnit and maintains a few other libraries.

Jose Muanis Castro holds a degree in information systems. Originally from the sunny Rio de Janeiro, he now lives in Brooklyn with his wife and kids. At The New York Times, he works with recommendation systems on the personalization team. Previously, he worked on CMS and publishing platforms at Globo.com in Brazil.

Jose is a seasoned engineer with hands-on experience in several languages. He's passionate about continuous improvement, agile methods, and lean processes. With a lot of experience in automation, from testing to deploying, he constantly switches hats between development and operations. When he's not coding, he enjoys riding around on his bike. He was a reviewer on the 2014 book, Mastering Unit Testing Using Mockito and JUnit, Packt Publishing. His Twitter handle is @muanis.

I'm thankful to my wife, Márcia, and my kids, Vitoria and Rafael, for understanding that I couldn't be there sometimes when I was reviewing this book.

John Piasetzki has over 15 years of professional experience as a software developer. He started out doing programming jobs when he was young and obtained a bachelor of science degree in computer engineering. John was fortunate enough to get his start in programming by contributing to WordPress. He continued by working at IBM on WebSphere while getting his degree. Since then, he has moved on to smaller projects. John has worked with technologies such as Python, Ruby, and most recently, AngularJS. He's currently working as a software develope...