This is what I do as well. I use VCS but it's more work. If I'm just refactoring a piece of code I comment it out while I work on the new stuff and test it. It

This is what I do as well. I use VCS but it's more work. If I'm just refactoring a piece of code I comment it out while I work on the new stuff and test it. It also has the added benefit that I can reference the old code easily if needs be. Occasionally I will commit with the commented code still in place (until I'm 100% confident with my new code) but I usually follow that up quite quickly with a commit removing it.