Application support teams who are maintaining pre-written applications may be disappointed to find that test cases have not been written prior.
The recommendation is not to stop work and start writing test cases.
Instead, test cases should be written incrementally.
Every time you need to “touch” the application code, you should write the test cases directed at that aspect. For example:
- Every enhancement to the system should be supplemented with newly created test cases
- Every bug you attempt to fix should be supplemented with pre-fix and post-fix test cases
In so doing, the risky and unstable portions of the system will be covered by test cases. At the same time, if test cases are regressed, a previously fixed bug will not resurface!