It wouldn't be all that surprising to see Poland and Finland doing atmospheric tests in the next few months. Given that Ukraine gave up their weapons for a totally vacuous security guarantee it would make sense for them to build bombs too. 2025 could be the year of global nuclear proliferation.
In fact, while most nuclear powers have dabbled in the idea of 'how could we conceal a nuclear test', it seems that only Israel is capable of doing it. That is an argument from the absence of evidence unfortunately.
Only because the US decided to officially look the other way. See "The Vela incident" which was never publicly attributed, but was almost certainly a joint Israel-South Africa test.
Exactly what weapons they have seems to be tied to the deals of the US-UK defense agreements. The UK's development of fission weapons is well documented. The development of thermonuclear is unclear and its not exactly obvious when and how they tested proper thermonuclear weapons.
Pakistan probably had nuclear weapons decades before their official tests. The US even made them one heck of an offer to maintain this policy of uncertainty. Ultimately they would debut very small thermonuclear weapons. They probably can manufacture large scale nuclear weapons into the megaton range. Pakistan probably also has plenty of delivery options. But ultimately their arsenal is mainly just there to deter China or India's territorial expansion. Pakistan can't really threaten other nuclear powers and it seems unlikely that a country like France is just going to launch an invasion of Pakistan. So there isn't really too much reason to bother with more tests. Ambiguity is their ally.
Given the sensitivity of global seismometers, I don't think this is physically possible.
Maybe you could test one on the far side of the moon? :)
