The integrity of the hard drive? Writing data to it and reading it back is about the only option, while keeping an eye on the SMART data. I use badblocks for the read/writing, but dban can probably do something similar.
Reading/writing semi-random crap to the drive for a couple of days stands a reasonable chance of killing a dodgy hard drive. I've had it knock out a brand-new one, the replacement sailed through the test. So at least I know the new drive isn't faulty out of the box.
Beyond that, data I care about is on the zfs filesystem. It doesn't check the drive as such, but it does check the the data it is reading matches the checksum of that which it wrote previously. You can't have that if you're on windows.
I've had a thoroughly faulty USB stick hosting an operating system for a few weeks out of curiosity about how well zfs works in practice - I was very impressed. No problems at all until I tried turning it off/on without warning, at which point the system wouldn't boot from that usb stick. Imported the volume on a different system, repaired the files, booted as before. Magic.