I always like to test new config files before deploying them--with tools like
apachectl configtest and
It's rare that mistakes crop up, but catching them before deployment eliminates any impact. The one that has bit me in the backside several times is
/etc/network/interfaces; I can't seem to find a tool to test it, and restarting the network on a remote machine only to discover it's no longer reachable is quite annoying--especially when we use a lot of bonding and bridging.