It's not all that complicated.Do you mind sharing your stress test methodology?
Look at the SMART data and check the number of reallocated sectors etc.. If you see bad info here, they fail.
I run badblocks on them, letting it do the full 4 write/read passes. This takes days. Let it run. If badblocks reports errors, fail.
Check SMART again, if the data still looks good, run a SMART long test on them. This takes about 6 hours for these drives.
If SMART still looks good, you're probably good to go. I like to also create a ZFS mirror across all the drives, fill it up, let it sit, scrub, sit, scrub, and maybe delete it all and fill it again, depending on how trusting I'm not feeling about drives that day. The ZFS test is best done on the server they will live in. Mostly to test the cables, controllers, backplane, etc. etc..