What tests would they run on a real alien?

Algebra.

They should see if he can pass a Middle School Algebra test.
What?
I thought my Algebra teacher was a Martian, didn’t you?

That’s what I was thinking, except it was more along the lines of “Can you imagine if his skin was made of something ferrous?” 1, 2, 3 bye bye alien. I suppose then we could see his insides.

Hopefully someone would be smart enough to run him though a metal detector or just try sticking some big neodymium magnets to him first.

As long as we get his engine and weapons manuals.

I would be curious about their sexual, if any, arousal stimuli

First check for latex paint on the skin and contact lenses on the eyes. Having passed that, I immediately ask for a cure for cancer and synthetic gasoline that costs 1/10 the fossil kind.

“Okay Bob, turn your head and cough.”

nm