It seems like it could be tested by taking a sample from the device before it ran and another sample after it ran and compared their element/isotope ratios.Rossi did exactly that. His "before" sample contained Nickel, and his "after" sample contained Nickel, Copper and Iron. But they were all identical to naturally-occuring elements, with no signs of nuclear processes having occurred.
From Wikipedia:
As Ny Teknik reports, Peter Ekström, lecturer at the Department of Nuclear Physics at Lund University in Sweden, concluded in May 2011, "I am convinced that the whole story is one big scam, and that it will be revealed in less than one year."[22][23] He cites the unlikelihood of a chemical reaction being strong enough to overcome the Coulomb barrier, the lack of gamma rays, the lack of explanation for the origin of the extra energy, the lack of the expected radioactivity after fusing a proton with 58Ni, the unexplained occurrence of 11% iron in the spent fuel, the 10% copper in the spent fuel strangely having the same isotopic ratios as natural copper, and the lack of any unstable copper isotope in the spent fuel as if the reactor only produced stable isotopes.[22] Kjell Aleklett, physics professor at Uppsala University, said the percentage of copper was too high for any known reaction of nickel, and the copper had the same isotopic ratio as natural copper. He also stated, "Known chemical reactions cannot explain the amount of energy measured. A nuclear reaction can explain the amount of energy, but the knowledge we have today says that this reaction cannot take place."[24][23]A recent paper by Miley (PowerPoint) showed that their LENR experiments are producing 39 non-natural isotopes. Rossi's device is producing 0 such isotopes.
They were grants from the Super Nova that left all our stuff behind. They should still be relatively the same quantities per isotope yet today because they are stable isotopes. I think nickel has 5 and copper has 5.
So, you use tunneling and a Weak Force based process to convert a stable isotope of nickel to what? Is it going to be an unstable or a stable isotope of copper?
So, let's move on over to the world of the Strong Nuclear Force. It teaches us thatif you take a hydrogen warhead to smack atoms together you will get both stable and unstable isotopes of all sorts of things, and with the unstable items you will get different half-lives. Some of the stuff will decay down to some other stable isotope of a different atom before it hits the ground. Other stuff won't.
This was common knowledge back during the 1950s when they were doing atmospheric nuclear tests all the time. They taught about it in gradeschool. We had gigantic wall charts available to tell us what was happening and WHY WE COULD NOT EAT POTATO SKINS.
Did they give that stuff up or something?
Knowledge of what is possible with the Weak Force is pretty thin in contrast. That's mostly because we haven't been studying it. No money in coming up with Nuclear stuff that doesn't blow things up eh!