Unfortunately, even with full testing and good quality control, some items arrive with the customer DOA, this can occur for a number of reasons.
A poor solder joint might appear visually OK, and conduct fine when placed in the test jig, only to fail later after the vibrations and shocks of transportation. When purchasing parts or spares of low monetary value, i usually but two or three (or perhaps 5 or 10 if the cost is very low).
This covers for the occasional failure in shipping and gives me more options if I screw up the first time.
I have only encountered a few issues with items over the years and in the majority of cases the supplier resolved them to my satisfaction.
I could go on a rant about the few who have not, but I don't want sued by DHL, Homebase or any of the others, I simply don't use them any more.