14:13 And whatsoever ye shall ask in my name, that will I do, that the Father may be glorified in the Son.
14:14 If ye shall ask any thing in my name, I will do it.
You're telling me that there's no tests for this? That somehow it's utterly impossible to make a coherent way of determining whether all prayers, in Jesus' name, are answered in the affirmative?
According to some billboards, Judgment day is in May of this year. I think May 21st. This is the return of Jesus and the whole flying around thing. This is a supernatural claim. Am I really suppose to accept that there's no conceivable way to check that? Not even on the 22nd?
I freely admit that one could change their claims indefinitely and never stake their belief on the latest nonsense they've pulled out of their hat. I cannot truly establish that disease isn't caused, as the Bible says, by sin or demons. But, I can establish that whatever these demons could do it's a moot point compared to germs. Just as I can show that invisible chariots would need to do no work because I can explain the motion of the stars with gravity (and I confess due to the nature of the analogy requiring an assist by dark matter). One could forever change their explanations, but that's not a requirement of supernaturalism. One could argue thusly that the moon is made of bananas with equally slippery supposition and layers of conspiracy. And nobody grants that that claim is supernatural. The fault lies not with the ability to test supernatural claims (after all, most every natural phenomenon from tides, to seasons, to healing, to weather, was supposed supernatural at one point), but with the ability to change ones claims as easily as clothing. Science can test reality, and if supernatural effects are part of reality then they can be established scientifically. It isn't a shortfall of science or the slippery nature of supernatural claimants but rather that reality shows nothing demonstratively supernatural about it. If fairies at the bottom of my garden were pushing up the daisies, we could well find evidence. We could also suppose magical reasons why the evidence didn't exist ad infinitum, but it doesn't really negate the original claim. It still becomes less likely to be true and more precarious to establish. And since we're talking about evidence and not absolute proof, it a serious problem. Testing supernatural claims, makes them less likely, even if they make up something new (and the fact that the way the do this is ad hoc confabulation rather than any sort of observation or perception of reality).
I'm not yoking the supernatural with scientific reason, I'm pointing out that if it matters with regard to reality, then science is the best and only real way of deciding the question. The only way the supernatural escapes science is by not being part of reality, that may well be the case, but it doesn't preclude science testing whether it is the case. You can argue a claim into such vagueness that it no longer matters, but it can't both matter and be scientifically untestable and undetectable. It must either be irrelevant or false, and if it's false it would necessarily be irrelevant.
I think you're giving supernaturalism far more credit that it deserves. It isn't something that's untestable and unfalsifiable, but rather something that we end up testing time after time and find it to be false. They make up something new, but it doesn't mean they weren't checked and found wanting previously. Supernatural claims have been tested and checked and phenomenon theorized, hypothesized, and understood for thousands of years (with a thousand year gap in there) and though religionists are always quick to open with "God did it" they have never ever been right in the entire history of the world. They always claim, initially, that it could only be the result of the supernatural and science has, thus far, always made them eat those words. Just because they backpedal, try to save face, regroup, and offer another steaming pile of shit at a later date, doesn't imply they weren't wrong each and every time they jumped to that same wrong conclusion by ignorance and faith. Given any reasonable scientific phenomenon, somebody somewhere claimed it was caused by supernatural forces; they were wrong. They've always been wrong. And claiming that it was because they weren't tested and found to be wrong is the utmost stupidity. You sacrifice the truth of scientific progress, naturalism, and empiricism in order to argue that they've never played some game properly because they play over and over and over and lose every time.