JUnit in Action SECOND EDITION PETAR TAHCHIEV FELIPE LEME VINCENT MASSOL GARY GREGORY ©2011 by Manning Publications Co. All rights reserved. Slides Prepared by: Dr. Samer Hanna

Needed downloads to run this book’s tests 1) Java 2 Standard Edition JDK Current version is JDK 6 update 22 2) Eclipse IDE Note: Eclipse documentation is available at:

PART 1 JUNIT ESSENTIALS Ch. 1 ■ JUnit jump-start Ch. 2 ■ Exploring core JUnit Ch. 3 ■ Mastering JUnit Ch. 4 ■ Software testing principles

Ch1. JUnit jump-start This chapter covers ■ Exploring JUnit ■ Installing JUnit ■ Writing our first test ■ Running tests

Introduction JUnit ( is open source software released under IBM’s Common Public License Version 1.0 and hosted on SourceForge JUnit quickly became the de facto standard framework for developing unit tests in Java. DEFINITION A unit test examines the behavior of a distinct unit of work. Within a Java application, the “distinct unit of work” is often (but not always) a single method.

Cont. By contrast, integration tests and acceptance tests examine how various components interact. A unit of work is a task that isn’t directly dependent on the completion of any other task.

Setting up JUnit In order to use JUnit to write your application tests, you need to add the JUnit JAR file to your project’s compilation classpath and to your execution classpath. Follow these steps: Download the JUnit distribution (junit-4.10 or newer) from Unzip the distribution zip file to a directory on your computer system In this directory, unzipping will create a subdirectory for the JUnit distribution you downloaded (for example, C:\junit4.6)

Adding junit-4.6.jar to our external jar files using Eclipse To run all the examples in this book we should tell Eclipse where it can find the junit-4.6.jar (or later) jar file and this is done by the following steps: Go to project menu Choose properties Choose Java Build Path Choose Add External Jars A Jar Selection window will be opened and you can browse to the folder where the junit-4.10.jar file is stored and select this file. Now you are ready to use JUnit

Testing with JUnit Example

The JUnit CalculatorTest program

CalculatorTest details At 1, we start by defining a test class. The only restriction is that the class must be public; we can name it whatever we like. It’s common practice to end the class name with Test. At 2, we mark the method as a unit test method by adding annotation. A best practice is to name test methods following the testXXX pattern.

Cont. JUnit doesn’t have method name restrictions. You can name your methods as you like; as long as they have annotation, JUnit will execute them. At 3, we start the test by creating an instance of the Calculator class (the “object under test”). At 4, as before, we execute the test by calling the method to test, passing it two known values. At 5, the JUnit framework begins to shine! To check the result of the test, we call an assertEquals method, which we imported with a static import on the first line of the class

assertEquals method The Javadoc for the assertEquals method is as follows: /** * Asserts that two doubles or floats are equal to within a positive delta. */ static public void assertEquals( double expected, double actual, double delta)

In the previous example, we passed assertEquals these parameters: expected = 60 actual = result delta = 0

Because we passed the calculator the values 10 and 50, we tell assertEquals to expect the sum to be 60. (We pass 0 as the delta because we’re adding integers.) When we called the calculator object, we tucked the return value into a local double named result. Therefore, we pass that variable to assertEquals to compare against the expected value of 60.

Cont. If the actual value isn’t equal to the expected value, JUnit throws an unchecked exception, which causes the test to fail. Most often, the delta parameter can be zero, and we can safely ignore it. It comes into play with calculations that aren’t always precise, which includes many floating point calculations. The delta provides a range factor. If the actual value is within the range expected - delta and expected + delta, the test will pass.

Summary Every developer should perform some type of test to see if code works. Developers who use automatic unit tests can repeat these tests on demand to ensure that new code works and doesn’t break existing tests. Simple unit tests aren’t difficult to create without JUnit, but as tests are added and become more complex, writing and maintaining tests becomes more difficult. JUnit is a unit testing framework that makes it easier to create, run, and revise unit tests.

Summary (Cont.) In this chapter, we scratched the surface of JUnit by stepping through a simple test. JUnit has much more to offer. In chapter 2 we take a closer look at the JUnit framework classes (different annotations and assertion mechanisms) and how they work together to make unit testing efficient and effective.