its just the Postoffice who insist on a unbroken supply
Lol, if I had a pound for every time I was told 'we can't knock the power off' I'd have retired years ago. Speak to the manager and remind him of his legal responsibilities to ensure safety of employees and the general public and tell him there will be a requirement for an arranged power down so he must just stop moaning and start making the necessary arrangements. You can also remind him that the testing will highlight most issues that could cause future power outages and instabilities so not allowing the power-down for full testing is actually shooting himself in the foot in the long run.