There are two tests that I do to test for sharp skates.
One is to rub your fingernail sideways ACROSS the blade (not lengthways). If sharp, there should be a tiny scraping of nail left on the blade.
The other test, perhaps more important, is to stand on the ice, feet parallel but about shoulder width apart, and try to push your feet out sideways. If sharp, the blades should grip the ice, if blunt they should slide sideways.
However, bear in mind that for your first couple of hours on the ice, you don't really want blades that are too sharp, since you will struggle to turn your feet. After that, you will appreciate the benefit of sharp edges.
Good luck anyway, I know you will be excited, lessons AND new skates ...
Derek