How should a user of OS X verify whether backed up data comprises everything required for lossless restoration? I'm most interested in approaches that compare both:


the original file
the backup


– after the time of backup. 

I'm aware of two approaches. Others will be appreciated. 



Less interested in approaches that verify integrity of: 


only the backed up file
only the file system used for backed up files
only the media used for that file system.
n8gray.org: Backup Bouncer

Improvements to Backup Bouncer were noted in March 2012 by Mike Bombich, developer of Carbon Copy Cloner.