I like to use a Light bulb ( auto type tester) and touch the center rail with one lead and leave it there. ....Now touch all the outside rails with the other lead to make sure the bulbs lights up . (except the short non derailing section)
ALL -Yep both sides on all track you can reach,
You can also reverse the process.... Clamp on the outside rail and check out the center rail for power.
Forgot to mention.... No engines or rolling stock on the track when testing.