Add test for DuplicateDetectionWrapper

Change-Id: Iff2d0c862e327ea3cc7dd08bf2d33c4cbd1f46a7
Reviewed-on: https://pirx.atteo.com/gerrit/447
Tested-by: Sławek Piotrowski <sentinel@atteo.com>
Reviewed-by: Sławek Piotrowski <sentinel@atteo.com>