How do you test a coil ?

You need to check that the coil is getting the proper signal to fire the plugs.

Pull the plug off of the coil and check for 12V on the B+ side of the plug. If not 12V, I would suspect the Engine Control Module which can be reflashed if you get the whole car to the dealer ( 1hr bill time roughly $100) or else I have been told that it could be the Ignition Switch.