How to test caterpillar c18 acert low oil pressure shut down

The engine Electronic Control Module (ECM) monitors the oil pressure on CAT engines. The Electronic Control System (ECS) for the engine sends the information to the GSC+P. Your setting yourself for extreme and quick success if you use a CAT ET(Electronic Technician)
http://www.empire-cat.com/catet/ Good Luck.

Since you want to test only low oil pressure shut down, so just use a trimmer and cat ET to trim down the pressure of oil to shut down setting and see whether the engine can be shut down according to the spec.

This is a critical element to protect the engine. Shop manual is needed. You can try manulslib.com but they may not have it.
So ask the dealer or MFG for one.