anchor.diff:    BankAccount = ?TESTED_MODULE:create(),
     ?TESTED_MODULE:deposit(BankAccount, 55 ),
     [erlang:spawn( fun () -> ?TESTED_MODULE:charge(BankAccount, 10) end ) || _X <- lists:seq(1, 10)],
  -  First = ?TESTED_MODULE:balance(BankAccount),
     timer:sleep(100),
     Last = ?TESTED_MODULE:balance(BankAccount),
  -  ?assert(First > 0),
     ?assert(Last =:= 5).
  
positive.code:   BankAccount = ?TESTED_MODULE:create(),
    ?TESTED_MODULE:deposit(BankAccount, 55 ),
    [erlang:spawn( fun () -> ?TESTED_MODULE:withdraw(BankAccount, X) end ) || X <- lists:seq(1, 10)],
    First = ?TESTED_MODULE:balance(BankAccount),
    timer:sleep(100),
    Last = ?TESTED_MODULE:balance(BankAccount),
    ?assert(First > 0),
    ?assert(Last =:= 0).
  
  charge_test() ->
  
negative.code: deposit_many_test() ->
    BankAccount = ?TESTED_MODULE:create(),
    [erlang:spawn( fun () -> ?TESTED_MODULE:deposit(BankAccount, X) end ) || X <- lists:seq(1, 10)],
    timer:sleep(100),
    Last = ?TESTED_MODULE:balance(BankAccount),
    ?assert(Last =:= 55).
  
  withdraw_test() ->
  