Using resettable fuses in place of single use - what make or break system to create??

Hi all, 

So I'm doing some testing and part of it requires checking what happens when certain pins are open circuit, shorted to gnd and shorted to 12v right ?

historically this was done with single use fuses (2a) but I want to use something resettable

So I've identified one tthat trips on 0.5A and has a withstand lf 100A, but how or what do I use for a make break indicator??

In line led I don't think I'd see quick enough, a potential divider then an arduino to read the analogue voltage maybe?

  1. Struggling with this one