[Galaxy Note II Android Development] jshare:
The best way to check if a backup works is to wipe your device and then try to restore the backup.

Of course, the hardest time to do this is the first time, because you're unsure of what you're doing, afraid of breaking something and don't yet have a backup to fall back on if the restore fails. But like anything, once you know what you're doing, there really isn't much to it.

I'm not familiar with CWM, having used TWRP %99 of the time (Philz recovery was the other), so you're going to have to search for instructions on that but:

If the backup fails, of course it isn't restorable and you shouldn't try

If the backup succeeds, it should be restorable *if* you backed up everything you needed to

On TWRP, a full backup is: EFS, Boot, Recovery, Modem, Cache, System and Data. Aside from Cache, you need all those things to do a full restore, so if the backup succeeded for all those things, you're probably fine to restore it. With TWRP at least, you can check the backup files to see if there are corresponding archive files for each of those things. A successful backup for me means 9 files in the corresponding backup folder, and you can also ask a CWM user how many files you should have so you can know in advance if you're missing something and save yourself a headache.

If anything is missing, you need to figure out why and only continue once you have a backup that isn't missing anything.

Next, once your most recent backup appears to be in order-

If this is your first restore, you actually don't know if any of your backups are good. Even if they each contain all the files, they could all be bad (although it's unlikely, which is a good thing). Regardless, prepare for the worst: before attempting a restore, make sure your recent backup is also copied off the phone, make sure that all your accounts (Samsung, Google, etc.) have synced to the cloud, export information to files that can be reimported (such as Wifi settings), know how to configure APN settings from your carrier, and finally, download a copy of your rom for reflashing if you need to start from zero.

Once you have all that, wipe system/data/dalvik/cache and restore your most recent successful backup.

If that works, awesome! You now have a backup you can always go back to, which will give you confidence about ever flashing anything on your phone, or even that it's ok if the phone itself needs to be exchanged.

If that doesn't work, reboot to recovery and try again or try restoring an older backup. And if none of your backups work and all you can do is continue booting into recovery each time, then reflash your rom, connect to wifi, and download Nandroid Manager. This is important. Use Nandroid Manager to restore your ANDROID ID from the most recent backup and reboot. Once you do that, the Play Store will recognize your phone and automatically restore all your apps. You can also use Nandroid Manager to restore call & message logs, apps & data, and more by extracting them from your recent backup. Once you're back up and running, you need to figure out asap why your backups are bad, correct the problem (change recoveries?) and then try again until you have a restorable backup.