When the backup is complete, test it by choosing a few random files or folders from the archive to restore. If your backup software has a Restore feature, use it; if not, select your former destination volume as the source. To test your archive, follow these steps:
Restore to a different location: You can usually restore files either to their original locations or to another location of your choice. For this test, restore your selected files to a different locationsay, your Desktop folder or another spot where you can find them easily.
Check the restored files: Compare the restored files to the originals using the Finder's File > Get Info command. Each pair of files should match exactly: same name, size, icon, creation date, and modification date. If the files were not copied to your selected destination or they are not identical, then either your backup software or its user made an error! Check your software's documentation, and if necessary contact the developer's technical support department for assistance.
Try an in-place restoration: Temporarily move one of the original files you backed up to a different location (again, the Desktop folder works well for this), then use your application's Restore feature to restore the file to its original location.
Check the restored files: Again, check each file carefully to make sure it is correct.
If the files are correct regardless of the location to which you restored them, your archive is working properly.
Although your initial test of a backup may succeed, it's important to test backups regularly to confirm that the archives are still intact, and that all the required files are being updated as they should be. If you're unaware of an error that has been preventing your backups from running properly for the past few months, the consequences could be severe. Get in the habit of doing a test restoration every time you change your car's oil or test the batteries in your smoke detector. By the way, if you haven't changed your oil or tested the batteries in your smoke detector recently... now might be a good time.