P.u/s
The answer for check rides is pilot under supervision in the majority of cases. Neither P1 or P2. Although if you reach the grade with a CFI during the flight he/she may allow you to continue the flight under P1 or P2. Only one pilot may be P1 at any time for the aircraft so that is a technicality debated between you and the other pilot and doesn't really matter which seat you sit in. Of course whilst you are P.u/s then the other person must be P1.