As said. coils are generally bomb proof and rarely give trouble if they are the correct one for the application. If they do fail it's usually caused by a broken internal wire which causes the coil to overheat. After coasting to a halt after this has caused the engine to stop for the first time you usually spend a frustrating half hour checking everything out with no result and then find the engine starts normally. If it happens again after about another 20 miles you can suspect a coil problem.
The following is a cut and paste from a pos to neg earth conversion article on a Lotus Cortina site which is interesting. It's certainly very easy to put the small coil wires on the wrong way round. Make absolutely sure you don't do it when using a Pertronix or it will be instant death for the module! I've done that but haven't done this test.
"Testing Ignition Coil Wiring Reversal."
You REALLY need to test this. With the ignition off, engine off, pull a spark plug wire loose from a spark plug. Place it loosely back in place.
Now start the engine. Hold a no.2 lead pencil carefully in one hand. With the other hand, pull the loosened spark plug wire slowly away from the plug. You shoud see a good size spark jumping from the wire to the plug. Now... CAREFULLY place the sharpened lead point of the pencil into the path of the spark... you should see a "flare" of particles flying from the pencil lead TOWARDS the spark plug. If you see a "flare" of particles flying from the pencil lead TOWARDS the wire... you have the coil hooked up backwards. Remove the pencil lead from the spark path. Replace the wire. Shut the engine off, and re-reverse the coil low-tension wires and re-test. Get it right!
Why does this matter? If you got this wrong, you will be losing about 50% of your voltage at the spark plugs! Weak spark! Essentially, if the ignition low tension coil wiring is reversed, the coil will... "pull" spark, rather than... "push" the spark. Electrons prefer to leave a high-temperature (high energy) surface (like the center electrode of the spark plug) rather than a low-temperature (low energy) surface (like the arm of the spark plug). More voltage (more spark) is available if the electrons move in the correct direction, in the direction they prefer, from the high-temperature center electrode of the spark plug to the (relatively) low-temperature arm of the spark plug. Test it! Get it right!