Parts fuel tank, how to test capacity before install?

Title. Looking for a replacement tank. Maybe it's an exercise in futility but I'd like to see what my options are before eventually swapping to a Gen 9 Corolla fuel tank. Is there a way to test capacity before installing a used fuel tank?

Can I fill it up with water then run the fuel pump to drain the tank. Then check how much was pumped out against the amount I put in? If good then fill up with premium and HEET to burn off residual water?

TIA

 

Ah, that's what I was trying to avoid -- using actual gas to test with no real way of safely disposing of possible contaminated gas.

for 50 bucks to remove a used one, I might try it.