These is no easy shadetree mechanic coil test.. unless you have a real ignition anylizer.. or other specialized equipment for testing a coil.. like . I think.. Bob on the N forum does.
In any case.. you can do a few basic tests, and make a few assumptions based on that after watching it in operation.
First.. test for pimary continuity... Use ohm meter on lowers setting and test between top post and the pigtail contact on the bottom. Depending on the sophistication and calibration of your ohm meter.. you may read anywhere from 1/2 to 2 ohms.. ( also depending on if you are testing a 6v coil.. or 12v coil ). Ohm meters are just not real accurate. Now.. if it measures anywhere close.. the primary at least has continuity.. though some windings may be shorted... etc.
Test secondary.. from top post to flat spring contact.. should be using the kohm scale.. Should read somewhere in the 4-8k range.
Best way to diagnose these is to get good points set at .015, and install it ont he tractor.. run a hot wire right to the coil top and check spark by bumping tractor over in neutral.
many spark problems are dirty connections and bad switches.. lastly.. bad coils.. etc.
T do a cheapy non scientific test on the condensor, take the lead on the condensor and touch it to its case.. now.. set ohm meter on lowest scale. and put leads across the condensor case and lead. Watch the scale on the meter... ( analog is best ).. It will swing from a low resistance to a high resistance ( as the cap charges.. and will show infinite or so.. when it is fully charged. )
Your tractor itself will be the easiest diagnostic tool to test that coil.. short of some specialized bench equipment.