I've broken the ring many times. From a hour or two when installing new switches to a week or so at a time when one of my guys drove a underground fiber warning post right through the fiber before it was fixed. Every switch that part of the network has passive fiber coupling, if the switch or power goes down the fiber is coupled together to keep the fiber live bypassing the switch. Also all are on large UPS's, IP accessible power strips, etc. Every pullbox for the fiber has at least 50ft spare cable looped in it.
The strange thing is the way different districts test things. The UPS's all have ethernet ports and are connected to the network. One district will test remotely once a month and send somebody out it it fails and another district actually have crews that go to the site to test the UPS and visually verify batteries are not bulging, connectors are good, etc on a monthly basis.