Having the DIS module tested by itself is OK and I do not discourage anyone from doing that. The DIS "system" tests I describe is intended to test the "system" (Distributoless Ignition System) from the HCU THROUGH the DIS module. You can check the CPS, CID, Coil power, etc. from the computer through the DIS to the individual component. It also tells you if you have a circuit or a connection problem. A DIGITAL multi-meter and a LED test light are all that are needed. The LED test light is not an absolute necessity but makes the CID test easier to do.
DO NOT use an analog (swing needle) meter, nor an INCANDESCENT light (or coil) tester on electronic components. These are OK for testing 12 volt components, such as light bulb circuits or power window motors, etc, but are not good for electronic components.
When checking for electronic component problems check all connections first. Make sure the connections are clean, free of corrosion, and snugly connected. Check for any bent, broken, or pushed out pins. Look at the wire connection to the pins. Again, look for corrosion or broken wires.
Once you are sure you have good connections, proceed to test the components. Remember, the components send signals to and/or get signals from the computer. Any breakdown or interference in this "communication" will cause problems. So, connections, connections, connections!
Note: the DIS module is grounded to the crossover tube by two of its screws (the botton two IIR). Make sure these are clean. Also the crossover tube is grounded by the two screws (bolts) that hold it to the heads. Make sure these are making good contact to the crossover tube, especially under the head of the bolts. It is a good idea to check all ground connections.