Yes, there is a test for Huntington's disease. All three of Woody's surviving children (Arlo Davy, Nora Lee, and Joady Ben) have been tested and have been found to be free of the disease. Two of Woody's other eight children, Gwendolyn and Susan, have already died from Huntington's. Woody's other three children perished from other causes, Cathy Ann in an apartment fire, Bill Rogers in a traffic accident, and Lorina Lynn also in a traffic accident. There was some suspicion that Bill Rogers Guthrie's death was a suicide, but there was insufficient evidence to confirm that suspicion. Bill died when his car collided with a train soon after he visited his dad in the hospital for the first time and saw Woody's hapless and hopeless condition.

--- Steve