On my RV, that is where I have tested to troubleshoot problems since I converted to an electric fuel pump. I remove the core with the proper tool and shove the test gauge hose on the fitting. 5-7psi is too much pre-filter on there for some reason. I guess it was timed at some point with a weak mechanical fuel pump, so I'm gonna install a low pressure regulator to further drop the pressure to like 2-4 psi to ee if that helps, until I can get the motor timed properly at 5-7psi without the regulator. I can't safety drive it on busy (even in rural areas) 75mph TX interstate with a top speed of 55-60 with the pedal to the floor, as it's acting currently without a pressure regulator. It had no speed issues with the old weepy mechanical pump. I stupidly never checked the pressure of that for comparison before I did the conversion.
If that's your only good place to test, it's better than nothing.