You are close. You first rub the berry on your skin (or leaf, or whatever). Wait 24 hours to see if a rash develops. Then you taste it, wait another 24 hours. Then you eat one, and see if you get sick after another 24 hours. Now you can eat several, and build up from there.

Yes, that is a lot of time to go hungry and testing just one item. And then you still don't know what actually gives you nutrition vs just not killing you (for example leaves that you can break down such as leaf lettuce, vs eating grass).

Alternatively, let the animals worry about all that and then just eat the animals.

Assuming this is in the context of some apocalyptic event requiring you to do this, relying on animal husbandry seems obviously wrong. Plus you only get ~10% of the energy from the lower trophic level.

The prevalence of meat comes from a society of abundance.

Evidence of early hominids and other less advanced proto-human or human groups shows a pretty significant amount of calories came from meat. Some suggest 60-80% of calories came from proteins, largely meat, at various times in history.

Example source:

https://onlinelibrary.wiley.com/doi/10.1002/ajpa.24247

A contradictory source says meat was less prevalent but still at 40-50%:

https://asu.pure.elsevier.com/en/publications/the-diet-body-...

Both of these estimates are way higher than what we know people eat today, where meat and dairy are 18% of worldwide calorie consumption (27% in the US).

So I think the abundance we see today is actually due to the availability of non-animal dietary sources.

That is the Universal Edibility Test and gets repeated ad nauseam in all the survival circles. You would miss out on some fine choice foods if you did that. Stinging Nettles (Urtica dioica) is one of them. Pokeweed (Phytolacca americana) too.

Source - used to teach these skills before it was cool to be a "survivalist" on TV and social media.

Yes I don't know how someone figured out that if you cook pokeweed and change the water multiple times then you can finally eat it without it killing you.