These are small tests. Similar agents might be, someday, delivered by bomblets or even aerial spraying. Every chemical and biological weapons treaty ever written has always been, and will continue to be, circumvented by the nations of the Shanghai Cooperation Org and Belarus.
I can imagine Al Qeida looking at aerial spraying of poisons or biological agents using a small plane. If you shoot them down you get both a marter and a devastating spread of the toxin.