>it's not a scientific test.

Isn't every subjective experience, almost by definition, unable to be tested scientifically?

We can objectively measure someone's brain activity during sleep, but we can't really measure their subjective experience. Implying that everything made up of subjective experience (like consciousness) can't be measured. Which also implies it can't be proven by scientific means. So in response to the GP comment, I'm not sure we can "know you're awake" (in the scientific sense, at least).