I think the easiest one is the fingernail test,, you can really tell the sharpness but I would suppose you would need someone to demonstrate it first with a dull, medium then scalpel edge.......
shaving hair is great too and even for me just checking the edge with my thumb,,,,, rubber bands is okay and maybe its me but I had blades that I personally thought could be sharper cut thru those bands so maybe they are sharp enough,,,,,,,,,, keep in mind that a lot of old schoolers say if the blades are too too sharp and the steel isn't perfect the edges will roll over when they come in contact with bone,,,,, hence magnus buzzcuts they don't feel that sharp but produce a lot of blood..
fingernail test for the beginners...