It's nearly impossible to shield yourself from changes to a code base. If the changes are extensive, it’s easy to get lost in a jungle of dependencies, or on a sea of broken code. Ultimately, you might give up, label the code 'legacy' and start lobbying for a rewrite.
Don't do that, come learn The Mikado Method instead. Learn how this systematic approach can be used to reclaim your code. See how you can visualize, prepare and perform business-value-focused changes without breaking stuff.
Recorded 2010-11-12 at Øredev - oredev.org