Another test:
Swap front tires side to side.
If the pull completely changes direction, then it is in the tires - a property called Conicity. You can only fix it by replacing the tires.
If the pull doesn't change at all, then it is 100% in the vehicle - usually alignment.
If the pull disappears or does change, but only a little, then it is both tires and in the vehicle.
Good Luck!!