Comment by gregopet

I've worked in projects where change was expected, so a policy of strict integration testing was introduced - test that treat the system as a black box and aren't aware of its internal structure (to a point, there is always some compromise). Every bug had to have a matching integration test. This made rewrites cheap, boring even (there is always _some_ danger of course, but the approach significantly simplified the decision to rewrite some part of the system or another).