Turn the lock in either direction five full rotations. Stop at exactly 50. Turn in the opposite direction. Slow down at about 45, and keep turning until you feel the first wheel pick up, probably at about 50-51. Note that number. Keep turning and again, around 45 slow down and note where the second wheel picks up, likely around 51-52. Take note of the number, then keep turning. Repeat until you have picked up all the wheels, noting the number. Finish with another full turn stopping at exactly 50.
Do the same thing as above, but turning in the other direction. The reason for the other direction is to check for sticking flys.
This is a good test because you can tell how many wheels are in the lock, therefore how many numbers are in the combination. You may find there is a broken fly, so no amount of dialing will open the lock. There are more reasons for the test, but you can find them in the safe section.
Gordon