I used to do IT for a certain pivate hospital group whom I will not mention (But who share the name of a famous english chef) .
We ran gen tests once a month, for each site, without fail. Everything critical had its own battery attached, so in the even that the gen set didn't fire up, we could flick back to the mains, and no one would notice.
There is no excuse for a multi million dollar data centre NOT doing this gen-set testing once a god damn month, especially if they are confident that their UPS system is up to par.
Here is a really easy system guys...
Step 1) Flick off mains
Step 2) See if the gen system kicks off
If Gen system fails
Then Turn mains back on AND fix gen system
Repeat until gen system works.
If your power systems are designed correctly, you should be able to do this, with no one the wiser, as your UPS will cover the 30 seconds or so it takes for your gen systems to notice the loss of power.
Generators can't just sit there until you need them. They are complex machines that need monthly testing and checking.
Can I have my multi zero consultancy fee please?
Mines the one with the pliers and the voltmeter in the pocket....