Failure Injection Testing

Happy-path tests do not prove recovery behavior. Deliberately exercise realistic failures before shipping destructive or stateful automation.

Minimum matrix

Inject at least the relevant cases:

• network timeout, truncated download, and unavailable dependency;
• permission denied / read-only destination;
• malformed or unexpected input;
• disk/write failure or partial extraction;
• child-process nonzero exit;
• interruption between backup and commit;
• retry after a partial previous run.

For each injection, require a clear nonzero failure, preserved prior state, actionable diagnostics, and a safe retry path. Verify temporary files and processes are cleaned up.

Never weaken production checks merely to make an injected failure pass.