Factory acceptance test (FAT) is an inspection and testing activity to check and make sure that the equipment has good quality (physic and work). This test can be done in the place that it is assembled or built.This test also to check and fit with specification of equipment. This test sometimes is done before equipment will be shipped.
Factory acceptance test have to be attended by user, vendor and customer. That is fair. Every one should know about status of equipment. Customer as buyer, user as people that use it and vendor as assembler or creator. All of attendant have to know and agree.
But this test not always have not to be 100 % clear, because suit with acceptance between vendor, customer and user can be tested again after arrive in the place, and vendor can repair and make sure again in other time.
This procedure shall be attended by vendor and customer, and have to accepted by both.
Below is a sample of procedure and guideline to do FAT, this is taken from http://www.sp.se.
In installation step, by contractor or anyone, this document have to be referenced and should be attached in dossier as a note of installation step.