To answer this question, I would like to share a real life experience of mine ( don't know if its the craziest one, still worth sharing, I guess)
My dad is a doctor and few years back he ordered a OMRON Blood Pressure Kit for his patients. The day we received the Kit, I tried it on me, my Mom and my Dad and then driven by my Tester instinct, decided to test the reading accuracy by validating it, by taking BP readings again using Hand held old style BP machine. I could see a deviation of 5-6% in both the readings. Repeated my test 3 more days- 3 readings for 3 different people, first using Digital BP machine (new one) and then using Analog BP machine (old style).
Finally I could establish a deviation of 5% in both the readings and then gave in a call to OMRON customer care and reported my test results with findings.
They agreed to the fact - few embeded systems in the Kit might be having an issue with exact readings, hence they were recalling those machines and offered us a next advanced and more accurate version as a replacement.
When we prepare a solution for users, it should perform in actual the way it is expected to - that's what a Tester tests and confirms!