Selective breeding is not mutation. Selective breeding is choosing for desirable traits from the natural variability of the species.
Some modern species are so different from their wild ancestors they are classified as separate species -- i.e., modern cows vs. ancient aurochs.
Dogs have been selectively bred from their wolf ancestors for at least 10,000 years and are considered a different species. Yet any wolf can breed with any dog and produce viable offspring.
The dog 10,000 years separated from the wolf has not evolved in to a different species. It is still a wolf. The dog removed from the influences of man would revert to its wolf form in a very short time. This is demonstrated on a nearly daily bases with feral dogs.
And, as for "testing" Darwin's theory, it's predictions are tested and confirmed daily by thousands of people who work in evolution related fields.
Strange that I don’t read of these developments. You should post them when you find them.
But a small number of mutation is inherent in every reproduction.
Most of these mutations are harmless or harmful, but if they are selected for -- by nature or humans -- then those mutations lead to speciation.
Any domesticated animal or plant is an example of speciation -- whether it is a separate breed (i.e., dogs), sub-species (horses) or species (cows vs. ancient aurochs).
Small steps toward some speciation naturally occur in every generation and such changes will either be selected for or against.
If for example, a climate grows slowly colder, expect larger animals with heavier coats to do better.
If we then analyze their DNA compared to warmer climate versions we will find both mutations and non-mutation related adaptions.
Pontiac: "Dogs have been selectively bred from their wolf ancestors for at least 10,000 years and are considered a different species.
Yet any wolf can breed with any dog and produce viable offspring."
Dogs are classified as a sub-species of ancient wolves, meaning they can and do still interbreed.
But cattle are classified as a separate species from ancient aurochs, meaning they still could interbreed but normally wouldn't.
The line between "can interbreed" and "can't interbreed" is usually the genus, as in African & Asian elephants.
They can't interbreed and so are separate genera.
But within the African genus smaller forest elephants are a separate species which could but normally doesn't interbreed with larger bush elephants.
Another example is humans and Neanderthals, once classified as separate genera, now found to have interbred and so now classified as the same species, circa 99.?% the same DNA.
Here's my point: speciation is a gradual process which can begin as quickly as a new breed of dogs but takes geological time periods for major changes in genus or family.
Pontiac: "The dog 10,000 years separated from the wolf has not evolved in to a different species.
It is still a wolf."
But the species of wolf which lead to dogs & modern wolves is now extinct.
So dogs are no longer the same species as their wolf ancestors.
They are still the same genus, so could interbreed under certain circumstances.
Pontiac: "Strange that I don’t read of these developments.
You should post them when you find them."
Just as you don't read about 100,000 daily airline flights with 5 million passengers around the world which land safely.
So how do you know they happen?
Well... once in a while one crashes and that makes the news.
The "big news" you'll see on evolution with be the day it's confirmed to have "crashed".
Never fear, I'll let you know when it happens.