apt possibly not updating broken counts/states correctly?

[Daniel Burrows <dburrows@debian.org>]

  Hi,

  Jiří Paleček writes on #457188 that there may be a bug in how apt
updates broken states in some corner cases.  I haven't confirmed this
myself or worked out a patch, but someone else may have time to verify
and/or debug it.

  btw, does apt have any sort of a test suite?  (e.g., using cppunit)
It would be nice to be able to accumulate examples of tricky situations
so we can verify that changes to the code haven't re-introduced bugs.

  Daniel