Testing router code before deployment

Just curious what testing protocol people use with router code (IOS or JunOS for example) when considering deployment of a new version. Obviously the deployment would be made incrementally, but I wonder if you do anything more than running it in a lab router for a couple of weeks before the initial deployment. Thanks -Tom __________________ Tom Holbrook Sr. Network Engineer Earthlink - Atlanta 'Safe?' said Mr. Beaver...'Who said anything about safe? 'Course he isn't safe. but he's good. He's the King, I tell you.' --The Lion, the Witch and the Wardrobe