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