How do I test the fuel pressure regulator

Many vehicles do not have a schrader valve. On those you use adapters to tap into the fuel system at the rail connection. Toyota calls them special service tools, but they are simply adapters. To release pressure on that system you pull the fuel pump fuse then start the engine and let it run until it stalls, then try starting it 2 more times, that will bleed off most of the pressure. Pressure wise you are looking for 44.1 to 49.7 psi at engine idle. Higher or lower could be a bad regulator, bad pump or system leaks.
Quick test for leaks it to run the engine, shut it off and watch the fuel pressure, it should stay at 21 psi or above for at least 5 minutes.
The pressure regulator on that vehicle is in the tank as part of the pump module.