[flatheadmurre]

The easiest way to make a "vibrator" coil tester is just any good quality dpdt (double pole double throw) relay.
One pole you use to ground the relay through the closed contact the other pole you use as your breaker points.
You need to ad a good quality capacitor over the contacts used as points !
The downside to this setup compared to using a distributor is you can´t adjust dwell to simulate the actual running conditions.