I just bought a brand new Hitachi brad nailer, and part of the "testing process" of ensuring that it operates as normal is when you get it, make sure it fires when the nose is depressed against a surface (among a few other things). One thing I'm not sure of is when you "test fire" this against a hard surface, whether it be wood or concrete, surely that's not good for the "hammer" in the unit, is it?
Don't dry fire brad nailers against anything you wouldn't drive a nail into. The instructions (PDF) specifically state, "against the workpiece," don't they? Use a scrap piece of wood for the initial testing. You may also want to limit dry firing to initial setup and any future troubleshooting procedures. Many newer nail guns have a dry-fire lockout that prevents the tool from firing when fasteners run out. This is partly to protect a workpiece from being marred by the hammer, and partly to extend the life of the tool.
Why would you test fire it against concrete? You bought a brad nailer, not a Ramset!