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xUnit Test Patterns: Refactoring Test Code Hardcover – May 21 2007
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From the Back Cover
Automated testing is a cornerstone of agile development. An effective testing strategy will deliver new functionality more aggressively, accelerate user feedback, and improve quality. However, for many developers, creating effective automated tests is a unique and unfamiliar challenge.
xUnit Test Patternsis the definitive guide to writing automated tests using xUnit, the most popular unit testing framework in use today. Agile coach and test automation expert Gerard Meszaros describes 68 proven patterns for making tests easier to write, understand, and maintain. He then shows you how to make them more robust and repeatable--and far more cost-effective.
Loaded with information, this book feels like three books in one. The first part is a detailed tutorial on test automation that covers everything from test strategy to in-depth test coding. The second part, a catalog of 18 frequently encountered "test smells," provides trouble-shooting guidelines to help you determine the root cause of problems and the most applicable patterns. The third part contains detailed descriptions of each pattern, including refactoring instructions illustrated by extensive code samples in multiple programming languages.
Topics covered include
- Writing better tests--and writing them faster
- The four phases of automated tests: fixture setup, exercising the system under test, result verification, and fixture teardown
- Improving test coverage by isolating software from its environment using Test Stubs and Mock Objects
- Designing software for greater testability
- Using test "smells" (including code smells, behavior smells, and project smells) to spot problems and know when and how to eliminate them
- Refactoring tests for greater simplicity, robustness, and execution speed
This book will benefit developers, managers, and testers working with any agile or conventional development process, whether doing test-driven development or writing the tests last. While the patterns and smells are especially applicable to all members of the xUnit family, they also apply to next-generation behavior-driven development frameworks such as RSpec and JBehave and to other kinds of test automation tools, including recorded test tools and data-driven test tools such as Fit and FitNesse.
Visual Summary of the Pattern Language
Refactoring a Test
PART I: The Narratives
Chapter 1 A Brief Tour
Chapter 2 Test Smells
Chapter 3 Goals of Test Automation
Chapter 4 Philosophy of Test Automation
Chapter 5 Principles of Test Automation
Chapter 6 Test Automation Strategy
Chapter 7 xUnit Basics
Chapter 8 Transient Fixture Management
Chapter 9 Persistent Fixture Management
Chapter 10 Result Verification
Chapter 11 Using Test Doubles
Chapter 12 Organizing Our Tests
Chapter 13 Testing with Databases
Chapter 14 A Roadmap to Effective Test Automation
PART II: The Test Smells
Chapter 15 Code Smells
Chapter 16 Behavior Smells
Chapter 17 Project Smells
PART III: The Patterns
Chapter 18 Test Strategy Patterns
Chapter 19 xUnit Basics Patterns
Chapter 20 Fixture Setup Patterns
Chapter 21 Result Verification Patterns
Chapter 22 Fixture Teardown Patterns
Chapter 23 Test Double Patterns
Chapter 24 Test Organization Patterns
Chapter 25 Database Patterns
Chapter 26 Design-for-Testability Patterns
Chapter 27 Value Patterns
PART IV: Appendixes
Appendix A Test Refactorings
Appendix B xUnit Terminology
Appendix C xUnit Family Members
Appendix D Tools
Appendix E Goals and Principles
Appendix F Smells, Aliases, and Causes
Appendix G Patterns, Aliases, and Variations
About the Author
Gerard Meszaros is Chief Scientist and Senior Consultant at ClearStream Consulting, a Calgary-based consultancy specializing in agile development. He has more than a decade of experience with automated unit testing frameworks and is a leading expert in test automation patterns, refactoring of software and tests, and design for testability.See all Product Description
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Top Customer Reviews
Then I bought XUnit Test Patterns by Gerard Meszaros. Wow! Finally the issues I've struggled with are being addressed. Okay, I must admit I'm not very plugged in to the online software development community, and I'm sure these issues have been discussed before. But this book looks special. I sense it's giving voice to these issues in a big way that's introducing many developers to these ideas for the first time. After all, it had to take time for this kind of book to be written. Time for the patterns to be developed through hard and frustrating work.
Rarely have I bought a thick book on software development and eagerly read every single word from cover to cover. But I have with this book. And I know I'll soon do it again. I'm even tempted to also purchase the PDF version of the book, just so I can reference it wherever I happen to be.
It's not the final word on AUT, but it has me embracing the ideal of TDD once more. The company I work for develops a huge OO-based enterprise software system with no automated tests. As Meszaros explains, this kind of legacy system is the most difficult for incorporating AUT (and daunting for those new to AUT). But at least now I feel like we have a good chance.
Even if you have done automated unit testing using any of the xUnit frameworks in the past, it will be useful to read the introductory narratives. Meszaros accomplishes the difficult task of clearly describing all of the aspects of xUnit including fixture management. I say "difficult", because it can be hard to document something that is so familiar that you do every day. Even though most of this content is not new, it provides clear terminology, which is valuable in making the rest of the book understandable.
Mezaros writes in a clear and highly detailed style and the book appears suprisingly free of typos and grammatical errors, which is a nice change for technical books.
Don't be scared by the size of the book. There isn't anything unnecessary here, and even the glossary is comprehensive and useful.
Most Helpful Customer Reviews on Amazon.com (beta)
Like Martin Fowler's Patterns of Enterprise Application Architecture, the book is split into two main sections, a narrative that weaves together a lot of the patterns and strategies, and then a catalogue of individual patterns. Between the two, there is a catalogue of 'test smells', similar to the 'code smells' discussed by Fowler in Refactoring, which I would suggest can be read profitably with the narrative section, rather than used as reference material.
There are a lot of patterns here on the mechanics of xUnit, such as 'Test Runner', 'Garbage-Collected Teardown' and 'Named Test Suite'. I was a bit confused about who this material is aimed at -- maybe someone looking at porting xUnit to a new programming language would find it useful, but a lot of it is fairly obvious to anyone who's used an xUnit in a non-trivial fashion (and certainly, if you haven't done so, this book is not a format that makes for a good introduction), or requires playing against xUnit's strengths (e.g. not putting setup and teardown code in their eponymous methods), although there is good reason for doing so in some of the examples provided, such as databases.
Beyond this, there is some good stuff on design-for-testability patterns (e.g. dependency injection versus dependency lookup), value patterns to replace magic constants, custom assertions and custom creation and other utility methods to make the intent of tests more clear. This material, along with the test smells chapter, is where the real value of the book lies. It encourages the application of the same software engineering principles you would apply to your applications (encapsulation, intent-revealing names, Don't Repeat Yourself) as you would to your testing code, something that's surprisingly easy to overlook, at least in my experience.
Also, the material on 'Test Doubles' (mocks, stubs, dummies and their ilk) is extremely useful. It touches on designing with mocks only superficially, but it does provide a helpful taxonomy of what different classes of doubles do. Now, if only everyone would standardise on this nomenclature, it would make life a lot easier. I suggest we brandish this enormous book threateningly at anyone who refuses to toe the line, and that should do the trick.
Because, boy, this book is big (about 900 pages). To be honest, it's too big. I rarely complain about getting too much book for my money, but the likes of GoF, PoEAA and PoSA 1 manage to come in between 400-500ish pages, so there's no reason XTP couldn't. The advantage is that the patterns in the catalogue, which take up most of the space, stand alone, without requiring too much flicking backwards and forwards between patterns.
The disadvantage is that there is a lot of repetition, so unlike the three design patterns books I mentioned above, which I suspect most people read cover to cover (or maybe that was just me and I'm a complete freak), I would suggest only dipping into the catalogue as necessary. For instance, how much difference is there between the 'Testcase Class per Class', 'Testcase Class per Feature' and the 'Testcase Class per Fixture' patterns? Not a lot, as you might expect.
I definitely liked this book. I would have liked it even more if it came in at about half its size and I would have preferred more emphasis on test and assertion organisation than the mechanics of the xUnit framework, but maybe that would have been a different type of book to the one Gerard Meszaros intended. This is nonetheless a must buy for anyone who cares about unit testing.
When I became aware that Gerard Meszaros ' xUnit Test Patterns book was going to ship Friday, I ordered it for overnight delivery on Saturday. I read well over 200 pages yesterday pretty much at one sitting, contented with a book that will change the face of the software industry, just as JUnit and all the other xUnit family have fundamentally altered software development for the better. Its definitely a big book at 944 pages, but it's not a book of excess, unnecessary pages. Rather it shows how hard it is to write defect-free software and the depth of the work that people are putting into this endeavor. The book uses Java as the language which obviously is no hardship to the C# programmer. Like most of the sound practices that have been evolving in the last ten years, this work has been evolving out of the terrific Java community.
Just like their are Code Smells, there are Test Smells, and writing good test code is just as hard and as worthy as writing good production code. Meszaros categorizes Test Smells into ProjectSmells, BehaviorSmells, and CodeSmells. Particularly interesting is his discussion in this regard to the commercial "record and playback" test automation products that have given test automation a bad name in many circles with their tendency to create FragileTests particularly with regard to Interface Sensitivity. Like many others, we were drawn in, and spent and wasted thousands of dollars with a vendor and exhibiting extreme Interface Sensitivity with the user interface. Their interface was not only unable to "pick up" most of the controls we use but even minor changes to the interface can cause tests to fail, even in circumstances in which a human user would say the test should pass. This only goes to support the notion many of us have talked about here about factoring a UI into MVP or MVC and not having logic in the "presentation."
Meszaros goes onto to provide very valuable discussions of Goals of Test Automation, Philosophies of Test Automation, and a Roadmap to Test Automation. We talk about things like Tests as Specification, also known as Executable Specification: "If we are doing test-driven development or test-first development, the tests give us a way to capture what the SUT should be doing before we start implementing it. They give us a way to specify the behavior in various scenarios captured in a form that we can then execute (essentially an "executable specification".) To ensure we are "building the right software", we must ensure that our tests reflect how the SUT will actually be used." We also talk about Tests as Documentation.
The main part of the book, of course, is the catalog of the patterns. Meszaros has provided a tremendous service to our community by not only cataloging and naming much of what we do, but also providing excellent discussions of why and how we do those things. I think, over time, this will be regarded as a seminal work in Software Development.
Gerard documented these (and many more) smells and patterns to help you write better tests. If you have written tests, you have probably used some of them, but even then looking at the patterns described in this book will help you tune your technique. For example Custom Assertions should always take the actual and expected values as parameters, so assertMagicObjectsAreEqual(actual, expected) is good, assertEverythingIsAlright(actual) is bad. And now you have a name for this technique, which makes it easier to explain to your fellow developers what you are doing. At 800+ pages you are bound to find plenty of new techniques as well.
If you are worried that this is another work by the pattern weenies, rest assured. The book follows the very simple and pragmatic "How It Works" and "When to Use It" format also used by Martin Fowlers' Patterns of Enterprise Application Architecture.
Part 1 - The Narratives: A Brief Tour; Test Smells; Goals of Test Automation; Philosophy of Test Automation; Principles of Test Automation; Test Automation Strategy; xUnit Basics; Transient Fixture Management; Persistent Fixture Management; Result Verification; Using Test Doubles; Organizing Our Tests; Testing with Databases; A Roadmap to Effective Test Automation
Part 2 - The Test Smells: Code Smells; Behavior Smells; Project Smells
Part 3 - The Patterns: Test Strategy Patterns; xUnit Basics Patterns; Fixture Setup Patterns; Result Verification Patterns; Fixture Teardown Patterns; Test Double Patterns; Test Organization Patterns; Database Patterns; Design-for-Testability Patterns; Value Patterns
Part 4 - Appendixes: Test Refactorings; xUnit Terminology; xUnit Family Members; Tools; Goals and Principles; Smells, Aliases, and Causes; Patterns, Aliases, and Variations
Glossary; References; Index
Most of the books that cover xUnit software do so from the perspective of a technical manual. Everything is geared to writing the actual code for the test. Meszaros takes a different tack. He covers more of the "why" behind test writing in xUnit, as well as the basic patterns and principles you should be aware of when you're putting together your tests. People new to xUnit will throw together tests without much thought as to the structure and robustness of that script. Meszaros maintains that much of the same care that goes into writing and designing programs should also go into the test scripts. Patterns such as In-line Setup, Chained Tests, State Verification, and many others can adjust your whole mindset towards what makes a solid and maintainable test script that will serve you well both now and down the road when you have to make changes to the program (and add more scripts to your test suite). The book is set up such that you can scan for basic ideas, and then go back to specific patterns for more information as the situations and needs arise. With the use of both actual code and UML diagrams, it's very easy to catch the gist of each pattern, as well as seeing how it would actually be implemented. Very good stuff here...
If you practice test-driven development (and you should), you have no doubt worked with your particular xUnit variant. This book is the next step in your learning, and it will make you a much better developer and tester...
The book is rather voluminous, divided up into 3 parts. The first part, "The Narratives", is a refreshing lecture on the philosophy of test automation, a brief on test smells, test organization, and tests with external resources. Essentially an overview of several concepts involved in test automation.
Part 2, aptly titled "The Test Smells," covers some of the common test smells, such as "Hard-to-Test Code", "Fragile Test", and "Slow Test" just to name a few. These are organized in the format Symptoms, Impact, Troubleshooting Advice, and Causes, with the Causes section broken down by cause, with Symptoms, Root Cause, and Possible Solution listed for each. I was impressed with this section as I already recognized some of the smells, as well as having already applied some of the solutions listed in the past.
Part 3 is "The Patterns", which follows the form of most patten catalogs out there. This is the largest section as it makes up more than half of the book, covering a lot of a ground. The patterns are given in a similar form to the ones in PoEAA, and provide easy to follow examples and in depth analysis. I was happy to find myself applying two of the patterns in the section already on a current project.
Overall, great book. Highly Recommended. ;)
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