A method of operating a testing system comprising a plurality of testing slots. The method comprising: testing the testing slots; obtaining a current testing data from the testing slots; determining whether one of the testing slots is abnormal by comparing the current testing data with a former testing data; shutting down the one of the testing slots and sending a repairing notification if the one of the testing slots is determined to be abnormal; performing a confirmation procedure to determine whether the one of the testing slots is repaired to be normal; and restarting the one of the testing slots if the one of the testing slots passes the confirmation procedure.