A multi-pole circuit breaker having the same number of sensors and controllers as poles. One pole is monitored by a first sensor and a first controller, which are disposed on a first circuit board. Another pole is monitored by a second sensor and a second controller, which are disposed on a second circuit board that is cable-connected to the first circuit board. A ground-fault sensor monitors the sum of current flowing through the line conductors and a neutral conductor, and the output of the ground-fault sensor is provided to one or both of the controllers. Each controller is operable to detect arc faults on the respective line that it is monitoring, and at least one is operable to detect ground faults. A push-to-test algorithm is executed in relay fashion, with one controller executing the test before passing the result of the test onto the next controller, which in turns executes the test.