Stephen Vance - Quality Code: Software Testing Principles, Practices, and Patterns

ePUB is an open, industry-standard format for eBooks. However, support of ePUB and its many features varies across reading devices and applications. Use your device or app settings to customize the presentation to your liking. Settings that you can customize often include font, font size, single or double column, landscape or portrait mode, and figures that you can click or tap to enlarge. For additional information about the settings and features on your reading device or app, visit the device manufacturers Web site.

Many titles include programming code or configuration examples. To optimize the presentation of these elements, view the eBook in single-column, landscape mode and adjust the font size to the smallest setting. In addition to presenting code and configurations in the reflowable text format, we have included images of the code that mimic the presentation found in the print book; therefore, where the reflowable format may compromise the presentation of the code listing, you will see a Click here to view code image link. Click the link to view the print-fidelity code image. To return to the previous page viewed, click the Back button on your device or app.

Software Testing Principles, Practices, and Patterns

Stephen Vance

Upper Saddle River, NJ Boston Indianapolis San Francisco
New York Toronto Montreal London Munich Paris Madrid
Capetown Sydney Tokyo Singapore Mexico City

Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals.

The author and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein.

The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales, which may include electronic versions and/or custom covers and content particular to your business, training goals, marketing focus, and branding interests. For more information, please contact:

U.S. Corporate and Government Sales
(800) 382-3419

For sales outside the United States, please contact:

International Sales

Visit us on the Web: informit.com/aw

Library of Congress Cataloging-in-Publication Data

Vance, Stephen.
Quality code : software testing principles, practices, and patterns / Stephen Vance.
pages cm
Includes index.
ISBN 978-0-321-83298-6 (alk. paper)ISBN 0-321-83298-1 (alk. paper)
1. Computer softwareTesting. 2. Software patterns. I. Title. II. Title: Software testing principles,
practices, and patterns.
QA76.76.T48V36 2013
005.14dc23 2013036018

Copyright 2014 Pearson Education, Inc.

All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtain permission to use material from this work, please submit a written request to Pearson Education, Inc., Permissions Department, One Lake Street, Upper Saddle River, New Jersey 07458, or you may fax your request to (201) 236-3290.

ISBN-13: 978-0-321-83298-6
ISBN-10: 0-321-83298-1
Text printed in the United States on recycled paper at RR Donnelley in Crawfordsville, Indiana.
First printing, November 2013

To my
for your continuous love and support.

To my parents
for preparing me for this and all other accomplishments.

Lean production has revolutionized manufacturing over the last several decades. Frameworks like TQM, Just-In-Time, Theory of Constraints, and the Toyota Production System have vastly improved the general state of automotive and manufacturing quality and spawned a vital competitive landscape. The family of Agile software development approaches brings the principles of Lean production to the knowledge discipline of software product development, but it needs to adapt these principles to a less mechanical context.

The idea of building the quality into the product in order to increase customer satisfaction and reduce the overall lifetime cost of maintenance has resulted in practices like test-driven development (TDD) and other test-first and test-early approaches. Regardless of which flavor you espouse, you need to understand what testable software looks like and master a wide range of techniques for implementing tests to be successful. I have found the gap between the principles and the state of the practice is often an unacknowledged source of failure in testing regimens. It is easy to say use test-driven development, but when faced with a project, many developers do not know where to start.

In showing people how to apply test-driven, or at least test-early, development, I often find that one of the obstacles is the mechanics of writing tests. Exercising a method as a mathematical function that purely translates inputs to easily accessible outputs is no problem. But much software has side effects, behavioral characteristics, or contextual constraints that are not as easy to test.

This book arose from a recurring need to show developers how to test the specific situations that stymied them. Consistently, we would sit down for a few minutes, we would write a unit test for the troublesome code, and the developer would have a new tool in his belt.