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Testing with JUnit
Testing with JUnit

Testing with JUnit: Master high quality software development driven by unit tests

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Profile Icon Appel Profile Icon Leonard Przybylski
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€10.99 €16.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3 (7 Ratings)
eBook Aug 2015 200 pages 1st Edition
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€10.99 €16.99
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Arrow left icon
Profile Icon Appel Profile Icon Leonard Przybylski
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€10.99 €16.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.3 (7 Ratings)
eBook Aug 2015 200 pages 1st Edition
eBook
€10.99 €16.99
Paperback
€20.99
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Free Trial
Renews at €18.99p/m
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€10.99 €16.99
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Testing with JUnit

Chapter 2. Writing Well-structured Tests

In this chapter, we're going to learn how to write unit tests with a clean and consistent structure by means of the four-phase pattern, and outline why it is important to do so. We'll be explaining the purpose of a fixture, and how to get a clear definition of the relation between a component's behavior and its verification. Furthermore, we're going to gain insight on what to test, where to start, how to continue, and how to know when we are done. We'll be concluding with a discussion on the pros and cons of various testing naming conventions. In a nutshell, we will be going through the following topics:

  • The four phases of a unit test
  • Choosing the next functionality to test
  • Getting the test names right

The four phases of a unit test

Well-written unit tests follow a clean and consistent structure based on four exactly defined phases. In this section, we will learn about the purpose of each of those and delve into some subtleties of fixture setup and result verification.

Using a common test structure

 

"A tidy house, a tidy mind."

 
 --Old adage

The attentive reader may have wondered why our first test setFetchCount was segmented by the use of empty lines. To answer this question, let's have an in-depth look at each of these segments with the first listing of this section, showing the common structure of a unit test. There are minor refactorings and additional comments compared to the version in the last chapter to emphasize more on the separation.

Note

Note how the constant NEW_FETCH_COUNT replaces the literal value assigned previously to a local input variable. Literal numbers often tell little or nothing about their purpose because they emerge from nowhere like...

Choosing the next functionality to test

Now that you know how to structure a test properly, you still might feel a bit insecure about what to test, where to start, how to continue, and how to know when you are done. What follows will be a few heuristics to help you in mastering these hurdles.

Start with the happy path

Meszaros defines the happy path as the normal path of execution through a use case or the software that implements it; also known as the sunny day scenario. Nothing goes wrong, nothing out of the ordinary happens, and we swiftly and directly achieve the user's or caller's goal, [MESZ07]. Regarding the addition of an item to our timeline functionality, the happy path is made up of an item that gets sorted into a list of existing items, and hence, gets depicted at the correct chronological position.

But what makes it so important to start with it? Because it delivers the highest business value, and gets us closer to the component's expected capabilities. Once we...

Getting the test names right

Finding good names is one of the challenges of crafting software. You need to find them all the time and for everything: classes, methods, variables, just to name a few. Because of that, the last section of this chapter explains the particularities of naming tests and balances the pros and cons of common approaches and conventions.

Test prefix

What makes a name a good name? To quote Uncle Bob:

"Three things: Readability, readability, and readability!"

He defines this later on as clarity, simplicity, and density of expression, [MART09]. Though this sounds reasonable, it leaves us with the question of how to achieve these qualities when naming our tests.

Before the arrival of annotations in the Java language, it was necessary to distinguish tests from ordinary methods to be able to process them by the JUnit runtime. This is because the latter has to pick up each test separately, run it, and report the results. The technical solution was to prefix the name...

Summary

In this chapter, we've learned about the structure of a well-written unit test. We've got to know how to use the four phases, that is setup, exercise, verify, and teardown, to map a single test to a certain component behavior. We've addressed the different techniques to set up a test fixture efficiently and illustrated the relation of a behavior to its verification.

Once we were familiar with how to write a test, we've been concerned with what to test. We've understood why we should always start testing with happy-path scenarios and do the corner cases later on. Moreover, we've been introduced to how code coverage can help detect holes in our safety net.

In the last section, we've discussed the pros and cons of the various test naming conventions. We've learned about the difficulties to map behavior verification into a meaningful name, and showed some possibilities to reduce a test name to the essentials.

The next chapter will evolve our example...

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Description

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.

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

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Publication date : Aug 27, 2015
Length: 200 pages
Edition : 1st
Language : English
ISBN-13 : 9781782166610
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Publication date : Aug 27, 2015
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Table of Contents

10 Chapters
1. Getting Started Chevron down icon Chevron up icon
2. Writing Well-structured Tests Chevron down icon Chevron up icon
3. Developing Independently Testable Units Chevron down icon Chevron up icon
4. Testing Exceptional Flow Chevron down icon Chevron up icon
5. Using Runners for Particular Testing Purposes Chevron down icon Chevron up icon
6. Reducing Boilerplate with JUnit Rules Chevron down icon Chevron up icon
7. Improving Readability with Custom Assertions Chevron down icon Chevron up icon
8. Running Tests Automatically within a CI Build Chevron down icon Chevron up icon
A. References Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

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Full star icon Full star icon Full star icon Full star icon Half star icon 4.3
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SuJo Sep 19, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I always appreciate a book that starts off with a 'Getting Started' section that actually get's you started but left out a huge history lesson. The first page clearly explains why unit testing is so important, and how regression occurs in projects. The first graphical depiction of a unit test was displayed around page 4, and was I the only person who spotted the depth of inheritance value of 2? That's superb! As for my favorite chapter it would be 2, and it's simply because it was the 'who, what, when, where, and why' chapter. It really set my expectations of the proceeding chapters, if I can understand what's suppose to occur than I can program for it to occur properly. The quotes throughout the book are neat as well, they break up the huge chunks of information that needs to be digested and are just subtle enough to not annoy you.By the end of the book you'll understand why unit testing is important, how to get started, and how to get some automated tests going while you sleep over night. The ebook edition has some nice color coded graphics that really speak to the text, I find this to be extremely helpful as well as mandatory. Final note: UML Diagrams.. absolutely satisfied these were used in the book! Highly recommend picking up a copy of this title and getting started with unit testing.
Amazon Verified review Amazon
Wayne Cannon Jan 23, 2017
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For an inexpensive book, this was surprisingly good.
Amazon Verified review Amazon
Sameer Jan 22, 2018
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excellent book , very engaging , enjoyed reading it
Amazon Verified review Amazon
Aleksandrs Kalinins Oct 31, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book is a good way to familiarize yourself with JUnit and some testing practices.
Amazon Verified review Amazon
Xanan Feb 04, 2017
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The book is a good introduction to Test Driven Development and Unit Testing.JUnit is discussed along the way to illustrate how it addresses various aspects of unit testing.The author does a good job at explaining the various concepts and presenting pros and cons of the various alternatives JUnit provides to achieve testing.More advanced topics like Runners and Rules are also covered.Mockito is introduced when test doubles are discussed and brief coverage is given to Hamcrest and AssertJ.API coverage is not exhaustive.Given the book size and its title, I did not expect to find a full chapter devoted to well structuring and properly naming unit tests and another one on continuous integration.Some parts of the book seem to be biased toward teaching how to do effective unit testing rather than actually using JUnit.The book subtitle "Master high-quality software development driven by unit tests" hints at something more than JUnit.
Amazon Verified review Amazon
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