An implantable medical device (IMD) includes one or more stimulation engines (SEs) and selectively connectable output switching circuitry for driving a plurality of output nodes associated with a respective plurality of electrodes of the IMD's lead system when implanted in a patient. The output switching circuitry may be configured to facilitate self-test mode (STM) functionality in the IMD (e.g., when it is in a hermetically sealed package) by using a dual mode switch in series with a stimulation engine selection switch with respect to each output node in the output switching circuitry under mode selection control.