Mushroom foraging isn't nearly as hard to learn as the general public believes, but you don't do it like this.
If it were just edible it would be labeled edible in the literature. If you consume it in a way or quantity that isn't recommended, well, there's a reason you don't see this stuff in the grocery store.
Big difference. It's not that all medicinal plants can be worse than the condition off the bat, it's that no one can make money by figuring out a dosage and putting it through the proper channels to allow manufacture and utilization for that purpose.
Herbalists have been doing their best to maintain a corpus of knowledge around these procedures for centuries. It isn't their fault that our boner for letting the market arbitrate ever aspect of our lives keeps useful research from being done.
Day 1: Eat a small (1/4 tsp) amount and observe for any reaction
Day 2: Repeat
Day 3: Don't eat any. Observe for any reaction.
Day 4: Eat
The explanation was that individuals can have widely varied reactions to species others find edible. Obviously don't do this for something unknown.