Java Power Tools

Part IV. Unit Testing

The next moment the day became very bothering indeed, because Pooh was so busy not looking where he was going that he stepped on a piece of the Forest which had been left out by mistake.

—“A Search is Organized, and Piglet Nearly Meets the Heffalump Again,” The House at Pooh Corner, A. A. Milne

Software development is very much a trial-and-error process, and it pays to proceed cautiously, little-by-little. This is why good testing is an essential part of the software development process. Although in practice it is often neglected, few developers today would deny the fundamental value of proper testing. Unit tests, especially when used in conjunction with modern agile development processes and techniques such as Test-Driven Development, have the potential to drastically increase the quality and reliability of your code.

Unit tests are also a very effective means of detecting regressions, especially when Continuous Integration techniques (Chapters 5, 6, 7) is being used. Whether you are adding functionality or refactoring existing code, a comprehensive set of unit tests provide a quick way of verifying that no existing functionality has been broken by recent changes.

Unit testing basically involves writing test cases to ensure that your classes function correctly. Unit tests are typically fairly low-level and modular—ideally, you should be able to execute a unit test in isolation, and not depend on any other test cases to be run beforehand. In other words, your tests ...