Abstract: A method and apparatus for testing a business machine of the type having a keyboard for entering data into the machine and includes means for storing the entered data. The method and test apparatus are directed to carrying out diagnostic routines on the business machine for determining the defective area of the machine. After the test apparatus is attached to the business machine, the data stored in the machine is transferred and stored in the test apparatus. A programmed control sequence of diagnostic routines is then carried out by the test apparatus with each routine terminating in the operation of an indicator member located on the test apparatus indicating whether a fault exists in the portion of the machine being tested. A control key on the test apparatus allows the operator to initiate a new diagnostic routine. At the completion of the diagnostic routines, the data stored in the test apparatus is transferred back to the business machine.