If they had one off the black market, they wouldn't test it. One would be hard to come by, much less two. When they develop a homemade weapon, THEN they'll test.
Why ruin the surprise?
With all due respect the reason why I think Iran does not have a weapon yet is because Israel would never allow it. Tel Aviv is ground zero, most Israelis know this, and the country's leadership is not going to stand by and allow Tehran to go nuclear regardless of what the rest of the world says (China and Russia for the most part).