This was somewhat of a false alarm. The problem was not that the
protocol implementation actually failed to round trip, but that two of
the fields were ignored entirely --- not serialized and deserialized at
all.
For reference, those fields were added in
fa68eb367e.
Continue with the characterization testing idioms begun in
c70484454f, but this time for unit tests.
Co-authored-by: Andreas Rammhold <andreas@rammhold.de>