XP junit tutorial using LinkedList

				See Readme.rtf for a 12 step tutorial on using junit.

junit provides a simple-to-use mechanism for testing each method in a class, and then a series of method calls to determine if the class is actually working properly. A LinkedList is a good example to use, as it is easy to have subtle errors. 

Each method should be 'challenged' with data and/or scenarios that might break the code. Boundary cases and typical cases should be coded. The developer codes assertTrue, assertSame, assertEquals, and assertNull statements for what is expected to happen. junit reports deviations, which represent errors. If all tests pass, a simple "OK" is reported.

Equally important, a junit test class simplifies regression testing to ensure that subsequent modifications don't break the code. It is all too common to do a fix or enhancement, and introduce new bugs. junit is simple enough to run many times per day.

Developers have been encouraged to have each class have a "main" routine that exercises the class. This generally makes shipped code larger, and is often left undone. junit involves standalone test classes that don't require any changes to the shipped code. Reflection is used to resolve method calls.