Mystery Shopper

Definition: a Mystery Shopper is a marketing practice in which people that are unknown to a shop, restaurant or other service provider are used to make a purchase and to describe their findings in detail.
MS can be used by market research companies, watchdog organizations or internally by companies themselves to measure service quality, customer services quality, or compliance to regulation, or to gather specific information about products and services.
Mystery shoppers perform specific tasks such as purchasing a product, asking questions, registering complaints or behaving in a certain way, and then provide detailed reports or feedback about their experiences.

More on mystery shoppers. More on customer services: Customer Service, SERVQUAL Model.