I've recently retired from retail after more than 20 years in the trade, and recent years have been made a misery by an increasing number of test purchases and police "popping in" to "see how things are". We were caught out in a sting once, due to an inexperienced member of staff serving a 15-year-old, and after that I made sure my staff were trained and trained again.
The worst thing, though, is the lack of a single approach by authorities when dealing with retailers . That leads to confusion and fear and has given me real problems in finding new staff over the past few years. At least Scottish retailers will know where they stand.