As I was reading today's NYT article on U.S. redesiging its nuclear weapons, I recalled a conversation with a senior Minatom official (retired by that time) about a year ago. I asked him if Russian nuclear weapon designers would need nuclear tests to maintain the current nuclear arsenal or to develop new weapons. He said that the weapons are being modernized without tests and he doesn't see any problems there. Even if it would come to developing mini-nukes, his sense was that weapons in the 10-100 metric tons range could be developed and deployed without new nuclear tests.
This doesn't mean, of course, that the Russia will not try to follow the suit should the United States resumes nuclear tests. It just that neither side really needs them.