You can observe for the presence of psilocybin by blue bruising of the mushroom flesh. If you make a tea, the water will turn blue as psilocybin converts into psilocin through hydrolysis. You can squeeze some lemon juice in to stop the reaction before it turns from blue to dark (i.e. adjust the pH to stop the reaction before the psilocin breaks down into non-active compounds).
Or you can just get some 4-Aco-DMT to convert to psilocin which is way easier to microdose.
Or you can just get some 4-Aco-DMT to convert to psilocin which is way easier to microdose.