Max, if the ovens in question are domestic type ovens in a workplace setting I suggest that the need to PAT and formally inspect can be simply avoided by replacing them at regular intervals. They are now so low cost that the cost of inspection/test makes little financial sense.

If however they are commercial/industrial ones than I cannot assist. No doubt there will be somebody else along soon who has better knowledge.

Max
From your posting I cannot work out what the issue is. If the microwave is being used in an office to for example warm up someone’s soup then it just needs to be part of normal PAT regime. If you or anyone is concerned over radiation leaking from the microwave, well don’t, since modern microwave greenly do not leak any energy unless they are damaged. If it looks damaged then chuck it.
The main risk if you are using a microwave in an office setting is people overheating the food; the classic mistake is someone trying to boil a liquid in the microwave. Often the liquid ends up superheated but not boiling until someone picks it up and it then boils over.