ashpan, UFO and jojo have both given valid comments. Like jojo pointed out, its about your work, its got be tested somehow, whether harsh or not. Besides, you're the one who knows more about what you've done, so just show potray that knowledge to them. I've been in that same boat before (not PhD) then i felt that my assessor was trying to catch me out but all i had to do was demonstrate my knowledge and it was fine. Best wishes