[BUGFIX] Tests: improve Mocking in ext:extbase

Unittests reveal some warnings which are caused by incomplete mocking.

Change-Id: I42089bb6c9016187d83382a2fa10450310993a84
Resolves: #56700
Related: #51436
Releases: 6.2
Reviewed-on: https://review.typo3.org/28370
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn