Bug 27837: Add unit tests

Bug 27837: Add unit tests

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Rhonda Kuiper <rkuiper@roundrocktexas.gov>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 99f67cb04c2bd03e9ac5c6d01688bf9520d10595)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>