How do i test the ignition coil to know if its good or bad

Easiest way without a meter or 12VDC tester, then simply pull coil wire out, insert screwdriver into distributor hole where coil wire was, then hold coil wire with pliers and have someone turn over engine while you hold coil wire close to screwdriver blade and look for a spark to ark from coil wire, if you see spark jump, coil is good, but only if it is healthy spark. If you have a meter, you can check to see that you are getting 12VDC to positive side of coil, most have red wire or plus sign at terminal depending on model and make.
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With the vehicle in 'Park'[Auto] or 'Neutral' and hand brake on [Manual], open the bonnet and locate the ignition coil.
1. Ensure the lead is fully engaged [and that all wiring connections are tightened and free from dirt and corrosion] then follow it to the distributor cap and check that the other end is properly connected and the plug leads are also.
2. Remove a spark plug lead at the plug then remove the plug.
3. Connect the removed plug to it's lead and while holding the threaded portion of the plug in positive contact with bare metal on the engine [exhaust manifold] have someone turn the ignition key to crank the engine.
WARNING: Be careful if the engine is hot and wear gloves and use pliers with insulated handles when holding the test plug.
4. As the engine is turning over inspect the spark plug electrodes for any sign of sparking. A blue spark is what you want to see. Orange spark or none at all is bad news for the coil which needs to be replaced.
5. When you're done, replace everything properly, account for all tools and remember a clean engine is a serviceable engine.

There are a couple of ways to test it. First if you have a multi meter set it on ohms and see if you have continuity. You can also try using a 9 volt battery with two leads going across the primary coil. You will have to touch the leads for only a half second and if it is working you will see a spark from the high voltage output if there is a wire going from it to ground but make sure that they are not directly connected just very close to each other