There is no accurate way to test what somebody's intelligence quotient is. Mensa is a group for people to feel good about themselves. In reality an IQ test is not a definitive measure of how smart someone is, how much they are capable of learning, or what they will accomplish in life.
I would join but i cheated to tell you this: take the answers off the first page you can get 19 without even knowing anything this is supposed to be a intellectual group right? Anyway I'm probably not smart enough I've never had an IQ test and I cant retake the test.
So there you go now you can make sure no one else cheats.