Saw a guy at the Davenport swap meet testing washers with a multimeter and a bucket
He had maybe 15 used machines lined up on a trailer and he was checking the lid switch and drain pump on each one before anyone could even ask a price. I've been hauling away junkers for 12 years and never once thought to bring a test bucket, I just load and pray. What's your go to quick check before you buy a used machine off some random guy in a parking lot?