anchor.diff:  %% completed.
   %%
   set_next_rebuild(T) ->
  -    put(T, hashtree:set_next_rebuild(get(T), incremental)).
  -
  +    put(T, hashtree:set_next_rebuild(get(T), incremental)),
  +    ok.
   
   %% Wrap hashtree:insert to (over)write key with a new hash to a single
   %% table and insert into the model tree.
  
positive.code:     end;
  %% After a comparison, check against the results against
  %% the ETS table containing the *snapshot* copies.
  postcondition(_S,{call, _, local_compare, _},  Result) ->
      Expect = expect_compare(),
      eq(Expect, lists:sort(Result));	
  postcondition(_S,{call,_,_,_},_R) ->
      true.
  
  
negative.code:          {trunc(math:pow(Width, Levels)), Width, MemLevels}).
  
  mark() ->
      %% frequency([{1, mark_empty}, {5, mark_open}]).
      ?SHRINK(oneof([mark_empty, mark_open]), [mark_empty]). % should shrink towards mark_empty
  
  %% Generate tree ids - the first one is used for the test, the others are added
  %% as empty hashtrees.
  