In fact, testing the software is not just there to make refactorings possible. The tests for the software are there to check if the software behaves correctly for a (hopefully representative) set of inputs. Thus, the check if a refactoring is invariant is mostly a side effect from having a test suite for your software, and thus, in my opinion, it does not matter how secure your recfactorings are. I do have my tests already! (And yes, I do consider it a heavy code smell if there are no tests written, because lots and lots of things are so very, very easy to test if structured ... if structured ok. not even well structured, just without hard-coded dependencies)