Yes they will know they are being watched and yes they will work -to the rules-. However, that in itself will throw up areas that the writers of the rules did not expect. Where the experts who wrote them always did something because they always did it and didn't think to put it in the procedures. I would like to think that the turn around procedures were fully checked initially and when the aircraft was handed over that the procedures on site were fully checked as part of the training. But 'like to think' is an assumption that is often unsafe. Even showing that when the procedures are followed repeatedly the problem does not occur is a useful result. I emphasize repeatedly because that repetition may not have occurred during normal testing.
I think that rather in the way there are fatigue test rigs that keep ahead of the aircraft in fatigue life to identify weak spots, perhaps battery fatigue rigs are needed that emulate a day in the life of a hard worked battery with all the pressure, temperature, charging and discharging cycles running at worst case.