I clean houses for a living, and one of my regular clients is a wealthy family whose enormous home takes me an entire day to clean. One morning, I found a note on the kitchen counter saying, “We placed 15 coins in hard-to-reach spots to test your work. Find them all.” Furious at being treated like a student taking an exam, I cleaned every corner of the house, checked behind radiators, under furniture, and even inside a light fixture, finding all 15 coins. I stacked them neatly on the kitchen table, placed my invoice underneath, and left a note reading, “All 15, feel free to check.” I also completed the feedback form they had left in a drawer. Later, the wife called me in a panic because her husband’s expensive watch had disappeared from the bedside table. I had discovered it behind the headboard during my search, carefully placed it in the top drawer, and left a note saying, “Found in one of those hard-to-reach spots.” She went completely silent before asking if I could return every two weeks. I agreed and doubled my rate. From that day forward, they never tested my work again.