Add unit tests to check if testlist will be expanded if a
subtest is blacklisted.

Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Reviewed-by: Kamil Konieczny <kamil.konieczny@linux.intel.com>
Signed-off-by: Petri Latvala <adrinael@adrinael.net>