Depends on what it is and what you know about it. If you advertise as new, you had better know that it is in fact new and never run. Even some new engines may be run at the factory. Some dealers test new engines before they sell them.
If it is a loco that is known to have problems, might be best to test before you sell. If it’s an old MTH PS1 loco, you need to replace the battery before you do that.
If it’s an MTH PS2 or older PS3, some buyers would welcome a photo of the hand held remote showing actual (near zero) miles and hours.
