Need advice on how to test my phone of defects

[anthony001]

im planning to do a meetup with an online seller and wanted to know what to check to make sure its not defective or anything like that

 

[GrippingSphere]

Phone Info to check if phone has original hardware, check IMEI.
CPU-Z to test all sensors if working.

Sent from my SM-N910G

 

[Ather]

Use the samsung service menu to test all the sensors, led, camera, speakers etc

Launch the Phone app and open the dial pad.
Type * #0* # (no spaces)