Several years ago I had finished an 8" bowl top and had it in the Cole Jaws finish turning the bottom. The bowl came loose from the little rubber buttons. The tool rest interfered with it popping off so the cole jaws just gave it a fling. It departed the lathe in a hurry--striking the ceiling behind me. It ricocheted into the far wall, came back and bounced off the table saw and landed at my feet. That day I ordered a vacuum pump and started setting up my vacuum chuck. Never lost another bowl that way. I wondered what would happen if there was a power failure but it never has happened. I found out what happens one day. I had finished a bowl bottom and in a Senior Moment I got the sequence wrong and turned off the vacuum pump before turning off the lathe. The bowl just dropped off the chuck onto the ways. No excitement--no damage.
My other "Poor man's stress test" happened while hollowing out a vase with a Forstner bit. The bit was held in a Jacob's chuck on a taper which fit into the tailstock. Forstner bits get hot and expand and sometimes bind on withdrawal. I usually back out frequently, blow the shavings out and cool the bit with compressed air. While woolgathering I was cranking the tailstock to back the bit out. What I failed to notice was that the bit was not backing but the taper was coming out of the tailstock. Suddenly there was a loud clatter-- the chuck and taper were slinging around striking the ways every revolution. I was afraid to cross the "throw line" to reach over and turn off the lathe. I ran out the back door, came around the shop and threw the breaker for the lathe. That is when I started using a draw bolt screwed into the taper and ending on the other side of the tailstock with a washer and a nut. Duh! I also wired in a stop button held to the right side of the ways with a magnet. Very handy.
If something can go wrong it eventually does.