There is provided a circuit with control function including a circuit to be controlled so as to be operated only if a predetermined environment meets a specific condition and being arranged to detect, in any predetermined environment, whether or not the circuit with control function is normally operated, and a test method thereof. The circuit with control function includes a controller (microcomputer) for operating the circuit to be controlled (a heater) only if a predetermined environment (ambient temperature) detected by a sensor (a first temperature sensor) meets a specific condition (0° or below). The controller includes a self-diagnosis device for diagnosing whether or not the circuit with control function is normally operated (step S5) and an interruption detecting device (steps S1 to S4) for detecting whether or not energization from a commercial power supply is intermittently interrupted in a predetermined pattern and activating the self-diagnosis device when the interruption of the predetermined pattern is detected.