- refactor tests
- add unit test on counting notes on a sheet

Change-Id: I6762a0e791a745b828800645effdfc044ac33710
Reviewed-on: https://gerrit.libreoffice.org/6954Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>