Provided is a method of operating a thermal bend actuator of a printhead nozzle arrangement of a printhead using an open actuator test circuit. The test circuit includes an open actuator test input, a column enable input and a row enable input; a drive transistor operatively linking said thermal actuator to a power supply; a bleed transistor arranged in parallel with the thermal actuator; a sense transistor operatively linking an output of the drive transistor and inputs of the thermal actuator and bleed transistor to a sensing node. The method includes the step of actuating the actuator to facilitate printing by enabling the column and row enable inputs to deactivate the bleed and sense transistors and to activate the drive transistor to link the thermal actuator to the power supply. The method also includes the step of testing the actuator's continuity by enabling the open actuator test input to activate the bleed and sense transistors, so that the thermal actuator is short-circuited and the sense node is pulled high if the integrity of thermal actuator is open-circuit.