Is Cygnus X-1 a proven black hole?

It seems to have passed all the know observational tests for a black hole, and to many, this constitutes acceptable proof until such a time as when new tests show this not to be the case.

It is getting harder and harder to find such new tests and at some point we will just have to throw up our hands and say its a black hole until new data indicate otherwise.

The consensus opinion by astronomers is that black holes are, indeed, real objects in our universe, and we find them in many different places based on the data that we have accumulated since the early 1990's.