There are lots of functions in the modern cellphone. I am sure they are checked on the factory (or by parts manufacturer), and I don't think people who refurbish phones test them all. Examples I can think of:

- Microphone and button on your 3.5mm jack

- Both Bluetooth data rates

- Every special function of MicroUSB connector (like MHT and whatever else you might have there)

- Second microphone (used for noise cancellation)

- Low-light camera performance

- Flash memory spare cells

- Thermal stability (does it overheat?)

- Battery capacity

- Every frequency band works

I can believe that manufacturer-refurbished phones are probably tested fairly comprehensively -- after all, the same people designed the original testing procedures.

But would an unrelated store do a comprehensive cell phone test? Or are they just going to turn the phone on, make sure that the screen looks fine, make a single call (in the nice, quiet office not far from the cell phone tower) and call it done? Somehow I suspect the latter.

I have bought a few used phones, and there is always something quirky that makes you wonder if you got a lemon. Sometimes it is just existing manufacturing faults, but how can you know?

An example: the WiFi connectivity is unexpectedly poor on a second hand phone, which could be caused by dozens of different issues, and some of those issues could be due to being dropped, liquid damage, poor remanufacturing, or component drift...

We bought a refurbished PC recently, and while upgrading the SSD, I noticed a shield around the CPU was completely misfitted: manufacturing fault or refurbishment error?