anchor.diff:  test() ->
   	remove_all(),
   
  -	T1 = add("0123"),
  +	T1 = add("0123"),		%% use default expiration limit.
   	ok = check("0123", T1),
   	ng = check("0124", T1),
   
  -	T2 = add("0123", -1),
  +	T2 = add("0123", -1),	%% set expiration limit (-1 means "already expired".).
   	ng = check("0123", T2),
   	ng = check("0124", T2),
  +
  +	ok = remove("0123", T1),
  +	ok = remove("0123", T1),
  +	ok = remove("0124", T1),
  +	ok = remove("0123", T2),
   
   	ok.
   
  
positive.code: 	{ok, V} = gen_server:call(?MODULE, {check, Id, Token}),
  	V.
  
  remove(Id, Token) ->
  	Reply = gen_server:call(?MODULE, {remove, Id, Token}).
  
  %%
  %% Utilities
  %%
  
  gen_token() ->
  	gen_token(get_unixtime() + ?DEFAULT_TOKEN_LIFE).
  
  gen_token(ExpireUnixtime) ->
  	integer_to_list(binary:decode_unsigned(crypto:rand_bytes(?BYTES_OF_TOKEN), big)).
  
negative.code: 	Val1 = impl_check_token(Pid, Id, Token),
  	{reply, {ok, Val1}, State};
  
  handle_call({remove, Id, Token}, From, State) ->
  	Pid = State,
  	BinKey = term_to_binary({Id, Token}),
  	riakc_pb_socket:delete(Pid, ?UTokenBucket, BinKey),
  	{reply, ok, State}.
  
  %%
  %% Implements: read/write tokens
  