How to make sure with Skype that the camera doesn't turn on iphone?

I'm going to be calling a friend but i need to make sure my camera is turned off from Skype. So they don't see me, how do i make sure it doesn't do that?

Don't turn it on…

Put something over the camera. That way you will 100% sure that even if the camera comes on by accident, they do see that you are really a man/dog/parrot with two heads, etc, etc…