The Tests were a series of protocols originally conducted in the United States in the 1800s to determine if someone was either a witch or possessed by a demonic spirit. When Teal'c of Chulak was put on trial due to being accused and also because he had a mark of the Devil on his forehead, in reality the symbol of his former Master. Apophis, Dr. Daniel Jackson mentioned this to Colonel Jack O'Neill and Captain Samantha Carter. (SG1: "Demons")