PAT or Portable Appliance Testing is simply the process by which electrical appliances are routinely checked for safety to ensure that any people, workers, or tenants who might come in contact with portable electrical appliances are not at risk of injury.
The 1989 Electricity at Work Regulations specify that:
“All [electrical] systems shall at times be of such construction as to prevent, so far as reasonably practical, such danger”
In light of this it is only common sense to carry out regular tests on all electrical appliances.