The lamp does not care which way the base is wired, but the accepted wiring method is to connect the "hot" wire to the center pin of the lamp base, and the "neutral" wire to the threaded shell for some safety.

I can see the logic of your guess on color coding (white=neutral, white/black=hot) but there are no guarantees that is how the previous electrician wired the house.

If you have a non-contact voltage detector, you might be able to tell which is "hot' when you hold the probe next to each wire when the switch is on. If they both test 'hot' try removing the lamp and trying again.

A regular voltmeter with leads won't do much good, since there is no real ground to measure each against.