Methods of operating integrated circuit devices are useful in testing impedance adjustment. Methods include connecting a node of the integrated circuit device to a first voltage node through a reference resistance and connecting the node to a second voltage node through a termination device, and comparing a voltage level at the node to a reference voltage for at least one resistance value of the termination device. When no available resistance value of the termination device generates a voltage level at the node that is deemed to match the reference voltage, the voltage level of the reference voltage may be altered, and the voltage level at the node may be compared to the altered reference voltage. When the voltage level at the node is deemed to match the altered reference voltage, the termination device may be deemed as passed. Otherwise, the termination device may be deemed as failed.