public void Balance_AccountOK() { //arrange Account account = new Account(); account.Operations = new List <Operation>(); account.Operations.Add(new Operation { Account = account, Amount = 10, Direction = Direction.Credit }); account.Operations.Add(new Operation { Account = account, Amount = 20, Direction = Direction.Debit }); account.Operations.Add(new Operation { Account = account, Amount = 0, Direction = Direction.Credit }); IRepository repository = MockRepository.GenerateStub <IRepository>(); ICustomerRepository customerRepository = MockRepository.GenerateStub <ICustomerRepository>(); IAccountRepository accountRepository = MockRepository.GenerateStub <IAccountRepository>(); IDtoCreator <Account, AccountDto> accountCreator = new AccountDtoCreator(); //act AccountServices services = new AccountServices(repository, accountRepository, customerRepository, accountCreator); decimal balance = services.Balance(account); //assert Assert.AreEqual(balance, -10); }