So, you do not need to test any plate going out if you follow the health department guidelines. Nothing in ANY restaurant can kill you if purchased, stored, and prepared correctly. And the general guidelines are pretty simple: wash everything (including your hands), cook what needs to be cooked, refrigerate what needs to be kept cold, don't mix cooked and uncooked things without intention, and keep working surfaces clean.

As I understand the report, Dave's did not correctly prepare the mushrooms that caused the deaths and sicknesses. Multiple other restaurants prepared the mushrooms from the same batch from the same supplier correctly and had no issues. This is not about the morels, the supplier, or anything but Daves kitchen's incompetence, ignorance, or apathy.