CFEngine's autonomous automation means that your policy, mistakes and all, will be duplicated quickly to all of your hosts. --- Potentially tens of thousands of them. When I taught martial arts it was humbling to watch a class of thirty duplicate my incorrect movement. I didn't know, because I didn't test myself. In martial arts I was simply embarrassed, but in configuration management, mistakes could cost me a raise or even my job. Testing is the paramount best practice for CFEngine. Let me tell you what I have learned.