If you want to sell second hand laptops then you need to make sure they are ok and there is nothign better than a checklist.

• clean fan
• check ram
• full hdd test
• wifi test
• test optical drive
• test battery
• wipe hdd (after grabbing drivers)
• run for 4 hours
• cpu test
• perhaps run burn in test pro
• graphics test
• run smart fan to check temperatures
• check SMART readings
• zero fill if required
• keyboard check with utility
• check mouse pad and buttons
• check power jack
• check power supply
• check plastics for damage
• check screen, pixel test, resolution test, blemishes and then grade
• hinge test, wobble, stiff, broken etc..