http://www.reuters.com/article/2013/02/12/us-korea-north-idUSBRE91B04820130212
Click the link above for the rest of the article.
I think its pretty safe to say that North Korea isn't testing nuclear bombs for nuclear power, they're testing bombs and missiles as an act of power. I would say I'd doubt they'd launch against anyone in fear of a nuclear counterattack, but North Korea's government has always been crazy.