...I've got enough to make 3. Let me waste a third of it to make sure the other 2 thirds is good. Yep...smart...smart dictator.</sarcasm>No. The test is NOT only to ensure that your material will fission. It is also a test to see if the mechanism works.
Of course, it's up to Saddam. He can either "waste" .33% of his fissionable material and KNOW that the bombs work
-or-
He can "save" all of the material and HOPE that the bombs work.
The same as deploying new systems in a production environment. You can HOPE that all the bugs are worked out
-or-
You can TEST the system prior to deployment.
Now, seeing as how this is an invasion of Iraq, Saddam would have to be an idiot to NOT test his weapons.
But you don't see that.
Now, how many bombs DOES Saddam have? An illustration of this is when we bombed Japan.