I've had a few nightmares with fuelpumps. One instance was an inertia switch in a Mustang. The switch exists in order to shut down the fuelpump in case of a roll over, or a severe impact. The problem with the switch was actually caused by an aftermarket stereo system (big boom box) located next to the switch. I've also had a Corvette that had an intermittent problem with fuel pressure. Turned out to be the regulator instead of the pump. But then a year later the pump went bad, intermittently too. The fuel pressure would drop 10psi and the car would run rough, just for it to clear up again. I know some fuel pumps also turn on for only a few seconds to pressurize the system until the car is running or cranking. They'll turn on, then off, and sometimes they get misdiagnosed as being bad because they are not running while being tested.
Just emphasizing that I know diagnosis can be difficult. Usually, I just jump the fuel pump directly where the terminals connect around the fuel tank, disconnecting everything electrically to the fuel pump but my jumper. I jump the pump on and test for fuel pressure. If okay, then I know it is nothing to do with the pump before it. Of course most dealership's have manuals that offer troubleshooting, providing a diagnosis tree.
G'luck and God bless,
William