libvirt/tests/domainsnapshotxml2xmlout/disk_driver_name_null.xml

<domainsnapshot>
  <name>asdf</name>
  <description>adsf</description>
  <disks>
    <disk name='vda' snapshot='external'>
      <source file='/tmp/foo'/>
    </disk>
  </disks>
</domainsnapshot>