Debugging and Unit Testing - Java 8 Recipes - page 381

eventually run with the project's own code and can then try to determine why the ex-
ception was thrown.
Note The Stack trace output will contain line number information if the program is
compiled with “Debug” info. By default, most IDEs will include this information when
running in a Debug configuration.
11-2: Locking Down Behavior of Your
Classes
Problem
You need to lock down the behavior of your class and want to create unit tests that will
be used to verify the specific behavior in your application.
Solution
Use JUnit to create unit tests that verify behavior in your classes. To use this solution,
you need to include the JUnit dependencies in your class path. JUnit can be down-
loaded from http://www.junit.org . Once it's downloaded, add the junit-
xxx.jar and junit-xxx-dep.jar files to your project or class path (where xxx
is the downloaded version number). When JUnit becomes part of your project, you will
be able to include the org.junit and junit.framework namespaces.
In this example two unit tests are created for the MathAdder class. The
MathAdder class contains two methods: addNumber (int, int) and sub-
stractNumber (int,int) . These two methods return the addition (or subtrac-
tion) of their passed parameters (a simple class). The unit tests (marked by the @Test
annotation) verify that the MathAdder class does, in fact, add and/or subtract two
numbers.
package org.java8recipes.chapter11;
import junit.framework.Assert;
import org.junit.Test;