To make sure it works.
Fence railing.
Hey, I try my hardest to understand your lyrics but I always fail. 
Are you even saying real words? 
Go to a track meet and announce a special race.
You might find it won’t work until its silver plated.
You know, Athletics Cup… Like America’s cup, Davis Cup … Melbournes Cup.
Actually handing it to the winner is optional… depending on the athletes you offer it to.
Go into a bar and say to the hottest girl there, “Hey, I just met you, and this is crazy, but how about a fuck?”. That ought to do it.
Over here we call it a ‘jock strap’ or a ‘box’. Maybe a ‘cup’ is too small for our athletes:)
To test things you should really subject them to forces greater than they are likely to face in use, to ensure they have a margin of safety.
So I have a cricket ball handy…
I was going to suggest a sledgehammer. While the cup was being worn, of course - have to test in situ, right?
Need a control group - once with, once without.
Good luck getting a volunteer for the control group.
Bonus points if your wingman is ready to record the testing procedure.
My brother always taped new cups to his forehead and then ran full-speed into the brick wall of our house.
Huh, I always thought that was some kid playing tennis.
It’s a pretty straightforward process really;
Strip down naked,
Fill the inside, convex part of the cup with TigerBalm gel,
Put the cup ‘on’, wiggling it around to make sure it completely encapsulates your genitals,
Tap (WHACK!) it reasonably hard from underneath with a ball peen hammer to see if there is any discomfort.
If no TigerBalm shoots out your crotch when you’re hitting it with a hammer then your junk should be good to go.
Do you have a friend with access to a grenade launcher?
If you have to ask, you don’t need one.
Record? I’d have that on social media less than a minute later. 
This is the method I use when I’m out testing cups.
Need answer fast?
Well in my day, the rookie got naked…and we also used blanks.
ETA: Dammit Drunky, I read the thread but didn’t click on your link until after I posted.