Unit testing legacy code

What is legacy code?
Some define legacy code as code without proper unit tests.

Consider these:

• Did you just write some legacy code yesterday?
• What happens when you are tasked to take over the maintenance of someone else's code; someone's legacy code?
• What happens when you need to modify someone's legacy code?

Some steps to take when planning to unit test legacy code:

1. identify the area of change
2. build safety net over the area before touching/ changing it
3. refactor the code to ease adding new code
4. write unit test for issue
5. write code for fix/ enhancements

Some links to refer to:

• http://members.pingnet.ch/gamma/junit.htm
• http://c2.com/cgi/wiki?UnitTestingLegacyCode
• http://spin.atomicobject.com/2008/12/29/testing-and-legacy-code-a-primer
• http://www.ibm.com/developerworks/java/library/j-testng/