I need to find a website that allows me to create online tests?

Well I found one but it doesn’t seem to do exactly what I want it to. The program has to be free, and require no downloading to use. I mainly want people to be able to sign up for the test without me having to put them in or creating a code for them, just setting one code. And i want it to be able to tell me who passed what tests. Any one have any suggestions?