Re: The
Systems need to be designed and configured to allow for manually triggering failover and failback.
Triggering it, running the failover system for a week (to include day/night and weekday/weekend) should be part of your monthly cycle. The same should hold true for any redundant ancillary equipment (e,g, ACs, UPSs).
Some things will never be anticipated but you can be better prepared for when they happen.