I'm sure that sly Kim has prepared another testing facility in a secret place - more spacious, with deeper and longer tunnels, better equipped and clean from contamination. (...)
Most likely Kim doesn't need new tests in the near future. Everything has been tested. (...)
As for 'denuclearization' then it will not happen anytime soon.
The whole process may fall down after the meeting between Trump and Kim if the US insists on very narrowly focused negotiations limited to the dismantling of North Korea's nuclear and missile program, followed by the US thinking about possibly removing sanctions on North Korea, if the US happens to feel like it.
I believe that genuine success will require broad ranging negotiations led by the two Koreas with the US, China, and Russia agreeing to go along with what those two decide. Japan's agreement would be convenient, but I don't believe is strictly necessary.
According to Moon's comments as noted in a previous post, genuine success is something that would take many years of sustained effort.