When a bug is
found tests are created to guard against it coming back. A bug in
production requires an acceptance test be written to guard against it.
Creating an acceptance test
first before debugging helps customers concisely define the problem and
communicate that problem to the programmers. Programmers have a failed
test to focus their efforts and know when the problem is fixed.
a failed acceptance test, developers then create unit tests to show the
defect from a more source code specific point of view. Failing unit
tests give immediate feedback to the development effort when the bug
has been repaired. When the unit tests run at 100% then the failing
acceptance test can be run again to validate the bug is fixed.