It's Monday in NK. No boom yet.
Not that WE know about anyway. I'm sure that as soon as it happens there will be a dozen or more governments around the world that will know about it through various monitering methods, but they might not tell us about it right away.
Perhaps the test was yesterday. More of a phhttt than a boom. Nobody wants to go down in that mineshaft, but the chief engineer automatically gets the short straw.