My accommodation run the fire alarm for a few seconds every week and Mr Roger is fine. He was afraid and disgruntled during the few days they did official fire testing (with some sort of implement to be attached to the fire alarms), but the fire alarm for the whole building only went off a few times for very short periods.
However, if the fire alarm does go off for a long time then their could be a problem. While this is purely anecdotal and could be false attribution, Mr Roger developed GI Statis shortly after a neighbouring flat set their fire alarm off (thus alarming ALL the flats in the building) for more than 15 minutes. We had to take him to the emergency vets and feed him hourly but he is fine now.
He’s also recently got used to the sound of bursting bubble wrap and doesn’t even jump. I’m not usually in when the fire test occurs but it’s possible he’s not so stressed about it anymore and recovers more quickly.