Scientists can't blow up a supernova in the laboratory. But they do have very detailed theories about how such things work, and they have made many predictions about what would be observed.
That is why Supernova 1987a was such an exciting event in the astronomy world. It was near enough that we could measure the details and test the predictions.
Unfortunately, supernova hunting is like fossil hunting: you find them when you find them. The supernova was already a few hours old before observatories were alerted. So, we didn't get to test some predictions about those first few moments. Maybe we'll have better luck next time. But the issue of luck in evidence-gathering doesn't make the predictions any less scientific.