Restoration testing

A backup that has never been restored is a hypothesis.

Until somebody has taken a copy and turned it back into a working system, all you know is that a job reported success. Plenty of organisations discover during a real incident that the backup excluded a directory, or the restore takes four days, or nobody knows the passphrase. Testing converts a hypothesis into a fact, and it is the only thing that does. It should be routine, and the interesting part is always how long it actually took.