Yes, it is scientifically testable. While supernatural entities are not directly testable, their manifestations in the natural world would be. So one would assume that if creation were true, there should be some evidence for it. The fact that there is no such evidence means, quite conclusively as far as I'm concerned, that it has failed its test.
I'll note that I diverge in my opinion on this from many highly respectable scientists who say it is not testable. That's a valid position, but one I disagree with. I do think the supernatural can fall within the realm of science as long as it is claimed to manifest in some way in the natural world. It would be easy for the creator to have left a signature in the genome, to create new species under observable conditions, or to otherwise leave some physical evidence. Because this is not the case, I claim it is testable, that it has been tested, and that it has failed its test.