Auto Level - How do I verify it is working

Hi Everybody,
I've been trying to figure out if my auto leveling is really working for the past couple of weeks and I haven't been successful. I have a RepRapGuru I3 with the BLTouch installed and everything seems to be working, the probe does its probing and I get fairly good prints. During the G29 command I can see the Z axis display is changing slightly at the various X,Y positions. During printing the LCD Z axis display does not change during a layer print; that is, it stays at the same number for the layer it is printing (ex: 1st layer is 0.13 during printing of the first layer). Is it suppose to be showing different Z axis positions during printing of a layer?

My main question is: how do I verify that the system is Z axis compensating during printing?

I had a hard time trying to word this question, so if needed please feel free to ask me for any clarification.
Thanks in advance for any assistance.

Print something similar to [www.thingiverse.com] and watch your Z axis to see if its moving up or down during the print. If your using the z axis compensation, you should see the Z axis move as it prints the extreme edges, or the center area (assuming your bed bows up or down in the middle)

Thanks PDBeal, I'll try it when I get home tonight

Tried the print, and the Z display stays at 0.13 during the whole print. It definitely is not adjusting since the print is good in some sections and bad in others.

My start G-Code is :
G28 ; home all axes
G29; auto level
G1 Z12 F5000 ; lift nozzle

I tried adding M500 but it did not make a difference