Do repair shops need to know my iphone password in order to replace the screen?

My dad has my phone and was asking me for the password because he claims that the repair shop needed it to "check that everything is working properly". All that they are doing is replacing my screen because it is cracked. I refused to give my dad the password and he got really mad. Is it really necessary for them to know my password just to replace a screen? Can't they just tell that it i working just by typing on the number pad? Or is this just a way for my father to try to dig in and snoop around through my phone?

They can't possibly test proper operation of the touchscreen (which is an integral part of the display), or really do a full colour test on the new screen, if they can only see the lock screen…

Idiot

This is for your protection as well as the repair shops. The only way for them to be sure that nothing else was wrong before the repair is to test the phone. Also if you come back with a problem afterward how do they know anything has changed? It would be like taking your car to a mechanic but refusing to give him the keys. You should probably just delete whatever it is you are trying to hide from your dad and re-install it later.