It makes me wonder what the message is for a real emergency. Also, the article mentions the day-shift supervisor thought the test was for the leaving night-shi

It makes me wonder what the message is for a real emergency. Also, the article mentions the day-shift supervisor thought the test was for the leaving night-shift operators, so he wasn't there to presumably tell his day-shift that there would be a test... but I think that this is not good for them to be warned ahead of time. You want them to be prepared to execute properly either way.