In reply to Hans:
Different people have different ideas about what testing a pair of shoes out on the wall involves. Clearly if you want to do a full climbing session, or try out a few routes and push the shoes to their limit you need to go to one of the many boot demos.
But a few minutes standing on real climbing holds and smears will cause minimal wear to the shoe and give a feel of what they will be like to climb in. Having worked in a different wall shop who offered a similar service to what the op had, a damp cloth will quickly remove chalk from the soles.
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