More specifically, we
are using the possibility to compare 2 versions of our code base. Then we focus
our efforts on reviewing and testing the code that has been modified or that was
added since the last release. My
experience always showed that the bulk of problems come from fresh code.
Of course, the preferred
way to avoid regression bug is to have a high automatic test coverage ratio on
the new code but it is rarely possible to have 100% coverage, especially on application with a complex UI.