Nowadays, the valid period for the passport seems to be 10 years, longer than that of before of 5 years.

Without a passport, you are able to register. But when registering, you are required to provide some information, such as the name and date of birth, to the GMAC, the information that should consist with the one in your passport. Therefore, if you are sure of the information that will be showed in you passport, then you may register the test before you get the passport.