If it short circuits, the circuit breaker on that circuit will open up and cut power within a couple of milliseconds, before anything has had a chance to catch fire. Though I definitely second the sibling comment about the multimeter.

I’m not so worried about a short circuit as much as putting a voltage on the case.

> Are there any tests which we can do on things to know that before turning them on?

Yes. Buy a cheap multimeter and test current flow on cables.

There's also nothing stopping you from buying a circuit breaker, fuse-holders and fuses if you want a little extra safety.

(When you google for those, combine with the term "DIN" or "Rail Mount")