Hard to check them with an ohm meter. When the finally fail and open up the windings then you will get no reading. The problem is the coil will discharge to ground before the time is right as the coil normal normal circumstances is hot all the time. The PCM will ground the coil when the proper spark time is due.
You could try pulling the coil out, connecting it to any of the coil wire plugs. The get a piece of wire, ground one end of it. Using the other end to "sniff" around the col body particularly at any cracks. If the coil is bad it will discharge. Look out for the the 20k volts though.