Yes, it's a theoretical problem. Of course it is impossible to test. But it needs not be tested by repetition. We can predict a phenomenon and see what happens when we set to prove it. If we ask the universe about a non-selfevident aspect and we ask it nicely (in proper mathematical terms) the universe will provide the answer. This is how we managed to have the universe reveal the Higgs boson. We used the right mathematics and initial conditions and the universe said, ok you leave me no choice but to reveal the particle, but only for an instant. And behold the previously never seen Higgs particle became observable. By changing a single value, the experiment would have failed.