Hi there as title really is it possible to test a coil pack to make sure it's working? As friend of mine has a 51 plate matiz which is jerky and down on power, coil pack has been swapped with second hand unit off eBay but obviously bit of a gamble wether that's working, also spark plugs have been swapped but still on original HT leads which will be the next idea I think any help much appreciated

My friends daughter had one of these and it had a similar problem but it was the distributor at fault. They are notorious for it apparently.