Abstract: Testing apparatus for an electronic ignition system for an internal combustion engine, the electronic ignition system having an ignition coil with a spark output, an electronic control unit connected to the coil for controlling the coil output, a distributor, and a magnetic sensor coupled to the distributor and to the electronic control unit and responsive to rotation of a timing cam in the distributor for producing output pulses for controlling the electronic control unit operation. The testing apparatus includes a pulse generator for generating pulses at a desired variable rate, driver circuitry, and a trigger coil inductor responsive to the pulse generator for exciting the distributor's magnetic sensor, whereby the sensor generates pulses as if the engine were operating for controlling the electronic control unit and testing its operation.