Today someone was caught in a shop, ringing up valid sales in the training mode at the point of sale. It's believed that they were doing this for a while and just keeping the funds so pocketing these undocumented transactions. He is not going to get away with it as sales are logged in the training system too.
However, as it is a good idea to have a training system available for both in house testing and training purposes, so we recommend that the training system should have its own password that way only people under supervision can use it.
Also what I recommend is removing the training mode icon off unsecured computers at the tills.