Frequent unit and integration testing is a theme of extreme programming. Unit testing is lower level regression testing while integration testing refers to testing the integration of major system components. I will not cover integration testing here.

Unit tests are often run automatically as part of the build process. The idea is that you can feel more confident modifying and refactoring your code, so you will not fear cleaning up code.

10.1 JUnit

Erich Gamma and Kent Beck wrote JUnit, a regression testing framework for Java development. I recommend using JUnit by either of these methods:

• Ant build targets
• Use the JUnit built-in support in your Java IDE

TBD