Yeah we test and tag electrical stuff, it's store policy. If it's mains powered and can't be tested (so it's safe to use) it can't be sold in the store.
If a relevant psu isn't available sometimes we keep a few things around until we can test them properly, but usually that's like a launch Xbone or a Gamecube etc. PS2 slims get turfed a bit (no psu), a lot of fat PS2's get turfed because the laser is dead.
I got a SFC untested a while back for virtually nothing as it was deemed rubbish (works fine). Got a few original Xbox consoles here that have DVD drive issues that were getting binned but they're otherwise ok.
Game carts usually just get sold on the assumption that they work if we don't have the console on hand, but yeah they're given a quick clean so they're more presentable.