Ensuring proper behavior of the base class lets comprehensive tests of
subclasses be simpler.
This also adjusts ApiFormatTestBase to be a bit more usable, passing an
array of options through to encodeData() instead of just a class name.
And removes the unused 'SKIP' from testGeneralEncoding, but allows
expecting an exception (for use in I63ce42dd).
Change-Id: Ib2a1fa0b04860b09105376881ff8411f9534c453
