CPE 102

Winter 2008

Lab 4



      None – any updates or corrections will appear here.







Ground Rules





You will be provided with a compiled (.class) file for a Java class called SomeClass.  This class has a single constructor (documented below) and an overridden implementation of the equals() method from Object.  Your job is to develop unit tests for the equals() method and discover several bugs that exist with its implementation.  Your knowledge of what the equals() method should do is vital to developing an efficient and exhaustive unit test.  Through lectures, your text, and the projects to-date you should have learned how a well-implemented equals method behaves – if you haven’t you should talk it over with your peers and/or your instructor before you begin to develop the unit test code.  Here is the documentation for the SomeClass constructor:



 * Constructor for SomeClass

 * @param x the x-value (may be any valid integer value).

 * @param y the y-value (may be any valid integer value).

 * @param s the String value (may be a String or null).



How to Proceed


  1. Think about the problem before you begin writing code.  What problems are you looking for in the equals?  How many different unit tests will you need for complete code coverage?  What cases should these tests cover?  Is there any way to organize the test code to make it thorough and concise?  Time spent up-front will usually save you time later!


  1. Create a new project in your chosen IDE and create a java class called SomeClassTest.  In a format similar to previous labs, create and run your JUnit test cases through a test driver named AllTests. For the time being, do not add any tests to SomeClassTest; merely compile it so you can see where your IDE places the .class files.  To do so, use Window Explorer and inspect your file system to see where SomeClassTest.class has been created.


  1. Place a copy of SomeClass.class in the same directory that your IDE puts its .class files for your project.  Do not write the SomeClass class – you must use the provided SomeClass.class file so that you can find the significant implementation errors the provided version contains.


  1. In the body of SomeClassTest, develop unit tests to construct various SomeClass objects (and other objects, if necessary) to test its equals() method.  The parameters to the constructor are provided in the Orientation section above.  You may write additional methods to facilitate testing if you wish.  Your code should handle (catch) any exceptions that may occur during testing.  Each unique unit test must have a meaningful method name and a javadoc comment that describes what the test is doing, for example:


 * Test to make sure the x instance variable is checked by the equals method
public void testXVariable()
   SomeClass sc1 = new SomeClass(1, 5, "Whatever");
   SomeClass sc2 = new SomeClass(2, 5, "Whatever");



  1. You should find at least three significant bugs with the SomeClass equals method.  Run them by your instructor when you think you have found them to see if they are the “right” ones.  If, after making a significant effort, you have not found three significant errors ask your peers and/or instructor for assistance.