Computer Science 507
Software Engineering

Spring 2013, The College of Saint Rose

Lab 6: Unit Testing with JUnit
Due: 6:00 PM, Monday, March 25, 2013

This week, we will work with the basics of the JUnit unit testing system.

You may work alone or in groups of 2 or 3 for these exercises.

JUnit Introduction and Setup

JUnit is a framework to manage test cases for Java classes. The idea is that for a Java class you wish to test, you write an additional class to perform the unit tests.

JUnit is often used with the Eclipse IDE, but can be used on its own or with other IDEs as well. You are welcome to complete this lab with any IDE you wish, but the instructions will assume you are running Java from the command line on If you wish to use JUnit in a different environment, you will need to set it up as appropriate.

To set up the Java environment on mogul to include the JUnit jar files. There is a script you can run to do this:

. /home/cs507/junit/junit.bashrc

Note: in the above, the period and space are part of the command and are important!

You can either enter this each time you log into mogul and wish to use JUnit, or you can add it to the end of the .bashrc file in your home directory.

Please copy the files and from /home/cs507/junit into a directory for this lab. These are an incredibly simple Java class and its corresponding JUnit test class. Take a look at these files and make sure everything in them makes sense (there's not much).

To compile these, since we are using a bit of a non-standard Java installation on mogul, we need to add the -1.5 flag to get a version of Java compatible with this version of JUnit. These command should work:

javac -1.5 
javac -1.5 

You can then run the unit test with the following:

java org.junit.runner.JUnitCore SuperSimpleTest

Question 1: What output do you get when you run the "SuperSimple" unit test? (1 point)

Now, change the isItSimple method so it no longer "works" (i.e., it doesn't return true) and recompile and rerun the test.

Question 2: What output do you get now? (1 point)

This example uses one kind of JUnit assertion, but there are many more.

Question 3: Write a new unit test class that creates a Java ArrayList, adds two items to the array list with the add method. It should then have assertions to verify that the two items are in the appropriate locations and that the size method returns 2. Include this test class and the output when you run the test in your submission. (5 points)

These kinds of tests work for many simple situations.

More Substantial Tests

Thinking about that ArrayList example, you will quickly realize that many tests will require some "set up" before and/or "tear down" after each test case. JUnit provides this capability with the @Before and @After annotations. The test method annotated with @Before will run before each test method (i.e., those annotated with @Test) and the @After method will run after each (whether the test succeeds or fails).

Note that you will need an additional import for each of these:

import org.junit.After;
import org.junit.Before;

Question 4: Make a copy of your ArrayList test from the previous section and modify it so that the construction of the ArrayList and the addition of the two items are in a method annotated with @Before (note that you will likely now need to declare your ArrayList as an instance variable), and separate out your ArrayList tests into 3 separate tests: one to check that the first element is correct, a second to check that the second element is correct, and a third to check that the size method returns 2. Include this test class and the output when you run the test in your submission. (5 points)

Question 5: Develop a Java class that implements a non-trivial data structure and/or algorithm, and a JUnit test class that tests the important features. Possibilities include a sorting algorithm, a list or tree data structure, or a class that performs some mathematical calculations that you can check easily. Submit your Java code for both the implementation and JUnit test class. (8 points)

Submission and Grading

To submit the assignment, send your source files and responses to the questions above to terescoj AT by 6:00 PM, Monday, March 25, 2013. Please include a meaningful subject line (something like "CS507 Lab 6 Submission").

This lab will be graded out of 20 points.