There's a theological doctrine called https://en.wikipedia.org/wiki/Eschatological_verification that claims that statements like "there's God" or "there's afterlife" are perfectly fine verifiable scientific statements, except that their verification come after death or Second Coming.
Your comment reminds me of it.
I think the test involves communicating your results. It's the same thing with the afterlife
Publish or perish made manifest.
Maybe it could be faxed back in time through a white hole?
"Remember kids, the only difference between screwing around and science is writing it down."