Every few years another “expert” on wild mushrooms dies from poisoning themselves by eating the wrong mushroom. They die painfully of liver, kidney, or heart failure.
There is no fool-proof test for differentiating edible and poisonous mushrooms. There are simply too many mushrooms species for any human to learn all of them — and the penalties for being wrong are often fatal. Experienced mushroom gatherers can pick mushrooms in their own local area fairly safely but even they cannot safely pick mushrooms in another region.
Identification of wild mushrooms is extremely difficult. People die every year by mistaking Amanita phalloides (Death Cap) for Amanita calytroderma (Coccora), Omphalotus olearius (Jack O’Lantern) for Cantharellus cibarius (Chanterelle), or Tylopilus eximius (Lilac brown bolete) for Boletus edulis (King bolete aka Porcini).
Worse, some mushrooms are only poisonous to certain people. Many people can eat the Tylopilus eximius (Lilac brown bolete) or Tricholomopsis platyphylla (Platterful Mushroom) without harm, while others will be poisoned. With over 60 varieties of poisonous mushrooms, even a true expert can have difficulty identifying them all.
Some survival writers will publish rough guides to which mushrooms might be edible and which might be poisonous. I will not. Do not eat wild mushrooms in a survival situation — it’s just not worth the risk.
The human body can exist a long time without food. Mushrooms have very little caloric content. Look at a can of mushrooms in the grocery store and you will see that the entire can contains between 35 and 70 calories. As a survival food, mushrooms are barely worth picking.