If you want to check if a coil pack is shagged, just start the car and one by one unplug the coilpacks, and listen to the engine idle - if it changes to a more lumpy sound (loss of spark in one cylinder), then the coilpack should be fine, and if it makes no change (had no spark to start with), then it is pretty likely to be stuffed (or the wiring to that coil). Make sure you plug each coilpack in before testing the next....