An air conditioner and a control method thereof. The air conditioner includes an indoor unit including an indoor heat exchanger and an indoor fan, an outdoor unit connected to the indoor unit and including an outdoor heat exchanger, an outdoor fan, a compressor, an expansion valve, and a four-way valve, and at least one processor configured to perform a test operation by controlling the indoor unit and the outdoor unit. Based on an outdoor temperature being less than a predetermined reference temperature, the at least one processor is configured to determine whether the indoor unit and the outdoor unit operate normally, by continuously performing a heating operation and a defrosting operation during the test operation.