*** TEST 21 ***
-----  TESTING THE NULL DRIVER CHECKS  -----
TA1 - rtems_io_initialize  - NULL DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_open        - NULL DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_close       - NULL DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_read        - NULL DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_write       - NULL DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_control     - NULL DRIVER RTEMS_SUCCESSFUL
-----  TESTING THE I/O MANAGER DIRECTIVES  -----
TA1 - rtems_io_initialize  - STUB DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_open        - STUB DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_close       - STUB DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_read        - STUB DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_write       - STUB DRIVER RTEMS_SUCCESSFUL
TA1 - rtems_io_control     - STUB DRIVER RTEMS_SUCCESSFUL
-----  RETURNING INVALID MAJOR NUMBER -----
TA1 - rtems_io_initialize  - RTEMS_INVALID_NUMBER
TA1 - rtems_io_open        - RTEMS_INVALID_NUMBER
-----  EXERCISE DRIVER REGISTER -----
TA1 - rtems_io_register_driver - RTEMS_INVALID_ADDRESS - NULL registered
TA1 - rtems_io_register_driver - RTEMS_INVALID_ADDRESS - NULL device
TA1 - rtems_io_register_driver - RTEMS_INVALID_ADDRESS - no callouts
TA1 - rtems_io_register_driver - RTEMS_INVALID_NUMBER - bad major
TA1 - rtems_io_register_driver - RTEMS_SUCCESSFUL - overwrite NULL
TA1 - rtems_io_register_driver - RTEMS_TOO_MANY - no slots
TA1 - rtems_io_register_driver - RTEMS_RESOURCE_IN_USE - major in use
TA1 - rtems_io_unregister_driver - RTEMS_SUCCESSFUL
*** END OF TEST 21 ***