As indicated, supernatural is not-natural. If science is limited to the testing and observation of natural things (matter and energy), then by that definition, the testing and observational techniques cannot be used to validate or negate anything supernatural ...
But it is a premise. You limit your testing to natural things only, do not have any tests outside of natural processes, and thus you cannot, by definition, have any other conclusions beyond something natural.
But this isn't so. Think of any miracle in the Bible let's say the bush in Exodus that "burned with fire, and was not consumed". Scientifically we could verify that there were indeed flames, and that the bush was not being consumed. And science would tell us that this was a a miracle, being a local violation of the laws of nature.
Indeed, the more scientific we are, the more clearly we can perceive this. Someone who didn't know very much about fire might think, "yes, it's an oddity, but is it a
miracle"? He might class it with other oddities like Old Faithful or an eclipse of the sun. But our scientific knowledge of fire would make us absolutely certain that we were in the presence of the supernatural. It is exactly scientific knowledge knowledge of the natural order of things that would allow us to detect the supernatural a violation of that order.
Edited by Dr Adequate, : No reason given.