This test checks that `mutation_partition::difference()` works correctly.
One of the checks it does is: m1 + m2 == m1 + (m2 - m1).
If the two mutations are identical but have compactable data, e.g. a
shadowable tombstone shadowed by a row marker, the apply will collapse
these, causing the above equality check to fail (as m2 - m1 is null).
To prevent this, compact the two input mutations.
Fixes: #8221
Signed-off-by: Botond Dénes <bdenes@scylladb.com>
Message-Id: <20210310141118.212538-1-bdenes@scylladb.com>
(cherry picked from commit cf28552357)