тайный покупатель
mistery shopper
https://books.google.com/ngrams/graph?content=secret+shopper%2Cmystery+shopper%2Cghost+shopper%2Cphantom+shopper%2Cmystery+consumer&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Csecret%20shopper%3B%2Cc0%3B.t1%3B%2Cmystery%20shopper%3B%2Cc0
