CentOS 7.x smartcl
Process for using smartctl is covered at Drive related information. Basically for long selftest use:
smartctl -t long <device_name>
Later status of test can be checked using:
smartctl -l selftest <device_name>
However as discussed at https://superuser.com/questions/766943/smart-test-never-finishes if drive is running into sleep issues and test is not finishing then use:
while true; do smartctl -a /dev/sda ; smartctl -a /dev/sdc; sleep 60; done > /dev/null &
If even after using above full test is not finishing with messages such "Interrupted (host reset)" or "Aborted by host" etc.. Then it might be issue with disk and it is likely that it will fail soon.