1. An implantable medical device, comprising: a neural stimulator adapted to provide neural stimulation therapy using either a first electrode configuration to deliver neural stimulation or a second electrode configuration to deliver neural stimulation; a controller operably connected to the neural stimulator and configured to select the first electrode configuration to control delivery of the neural stimulation therapy through the first electrode configuration; an electrode configuration tester for testing for a fault in the first electrode configuration during delivery of the neural stimulation therapy to a patient, the fault occurring when the efficacy of the neural stimulation therapy using the first electrode configuration is lower than a threshold; and the controller operably connected to the electrode configuration tester to repeatedly test the first electrode configuration during delivery of the neural stimulation therapy to ensure uninterrupted neural stimulation to the patient, and to respond to a detected failure in the first electrode configuration by selecting the second electrode configuration and controlling delivery of the neural stimulation therapy through the second electrode configuration.