What do you look for in a puppies crate training before you start leaving the house?

Hullo! Basically exactly as the title says.

Obviously I’m not about to leave for 3 hours or smth, just a test with going to the shop (5ish minute walk one way)

Is there something I should look for that indicates he’s ready to be alone? As long as he’s pottied he does fine in there I’m just worried that when I try to leave the house will be the time he freaks out.