What if you switch on ... but still haven't plugged into the mains?
An electrical safety test with no electricity involved what a perfect way to make sure everything passes and is "safe".
As to the matter of time....a good ES tester should be able to power the device on, then when it has booted you then start the tests in normal polarity. you then power it down, reverse polarity, boot the device and do the tests again. I was using a tester that did this well over 10years ago..... and what device takes 10minutes to boot? No modern stuff surely.
But yes there is plenty of old stuff around still.
But surely EST is about making sure the device is safe rather than cutting corners to tick the "I have done it" box in as short a time as possible.