Actually, it would be A Very Good Thing to know about nuclear weapons to have a meaningful opinion about effective nuclear proliferation. A ‘conventional’ nuclear weapon goes for heat and blast, where a ‘dirty bomb’ goes for radiation (and terror). Test bans are really good for helping to control ‘conventional’ weapons, since testing or substantial computer simulation based on real-world knowledge is important to design weapons to get the maximum (heat & blast) effects. They do nothing for dirty bombs, either those that are from a nuclear detonation, or those that have nuclear material packed around a conventional explosive. Control of fissile materials is critical for preventing dirty bombs, and detection is an important part of defense against them.