Bug 29936: Add unit tests

Bug 29936: Add unit tests

This patch adds a unit test for the new functionality introduced with
holds_get_captured allowing for holds to still be highlighted to patrons
at checkin but not mark them as found/transfered in the system.

Sponsored-by: Cheshire Libraries Shared Services
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>