Yes, Seamus, the power switch must be 'on', but that does not mean it gets 'powered-up' and 'functionally tested', it just gets a few microamperes at 500v DC up it.......
The principal reason for PAT testing seems (to me) to be to raise revenue for the Government by providing another ever-increasing pile of paperwork to be chased by civil servants, and more compulsory training to be administered by their 'quango's.....