This wasn’t a test run. The muslim tried to detonate explosives on the flight over Detroit and was stopped by passengers.
Why would you do a test run with fireworks and expose a weakness in the system? Wouldn't security then crack down and make getting real explosives through much harder?
Hate to sound conspiratorial, but it would make sense in a way that this was a failed attempt using a homemade explosive device and security is calling it “firecrackers” so travelers don't get upset and stop flying.