unittest for fdo#71434

Change-Id: I4ef376e048aa0ba37e5c1bc7664e9e8cd3e283b6
Reviewed-on: https://gerrit.libreoffice.org/6985
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>