anchor.diff:  %% Test cases
   -export(
       [ t_generate_and_store/1
  +    , t_fetch_expired/1
       , t_storage_error_corrupt/1
       , t_storage_error_io/1
       ]).
  
positive.code:     Secret1      = Secret2,
      Creds1       = Creds2.
  
  t_storage_error_corrupt(_Cfg) ->
      ok = oauth1_mock_storage:start(),
      ClientID = {client, <<"fake-client-id">>},
  
negative.code: groups() ->
      Tests =
          [ t_generate_and_store
          , t_fetch_expired
          , t_storage_error_corrupt
          , t_storage_error_io
          % TODO: Error cases:
          %   - string generation error (low entropy)
          ],
      Properties = [],
      [ {?TYPE_CLIENT , Properties, Tests}
  