Yea, Gab, with the B&S pump I have not seen any new ones fail...I was referring to the little square after market pumps. I believe that WMS is selling them now as a replacement for the Wip22/23 pumps.
What I have seen is that some leak (easily fixed with tightening the assembly bolts) or there is a piece of trash (plastic) caught in the pump that prevents it from moving. Again, easily fixed or simply toss it as inexpensive as they are.
Generally, these pumps are very efficient and don't just go bad on their own. If they get a bit weaker over time, they're still overkill as far as how much fuel they move.
A quick way to determine if the pump is working is to pull the fuel line off at the carb. inlet and try to start the engine. The fuel should shoot out of the end of the fuel line, (not just a dribble.) Now, that's not to say that you don't have a line kinked, fuel shut -ff problem, filter plugged, pick-up in the tank problem...but if you've got good fuel pressure at the carb. inlet, you know that everything before that is working as it should.