FAT vs SAT: what should each test prove?
FAT verifies what can be proven at the builder before shipment. SAT verifies the installed machine in the real site environment. They are complementary gates, not interchangeable names for the same test.
What belongs in FAT?
Build verification, functions available at the factory, controls, documented performance tests, interfaces that can be simulated, documentation, safety checks and shipment-release conditions.
What belongs in SAT?
Installation, actual utilities, site interfaces, upstream and downstream equipment, field devices, production conditions and requirements that cannot be reproduced meaningfully at the builder.
Why does the handoff matter?
The SAT team needs a clear baseline: what passed at FAT, what remained open, what changed after shipment and which requirements were intentionally deferred to site.