应用程序层单元测试在DDD中的外观如何？

在我的工作中，我们正在编写由应用程序调用的Web服务。我们正在使用域驱动设计以敏捷的思维方式进行工作。与DDD中一样，我们具有域和应用程序层。但是，在为这些层编写单元测试时，我们遇到了问题，因为似乎我们在域单元测试和应用程序单元测试中两次测试了域逻辑：

应用单元测试

    [TestMethod]
    public void UserApplicationService_SignOut_ForExistingUserWithBalance_ShouldClearBalanceAndSignOut()
    {
        //Arrange
        long merchantId = 1;
        long userId = 1;

        var transactionId = "001";
        var id = "122";            
        var user = Help.SetId<User>(User.Register(id, new DateTime(2015, 01, 01, 00, 00, 01)), userId);

        _usersDb.Add(user);
        var userBonusBalanceRepository = _testContext.MoqUnitOfWork.MockUnitOfWork.Object.GetUserBonusAccountRepository();

        UserBonusAccount uba = userBonusBalanceRepository.GetForUser(user);
        uba.PayTo(
            new Domain.Core.Money { TotalAmount = 10, BonusAmount = 0 },
            new Domain.Core.Outlet
            {
                BonusPercentage = 50,
                IsLoyalty = true,
                Id = id,
                OutletId = "111"
            },
            transactionId,
            DateTime.Now);
        userBonusBalanceRepository.Update(uba);          

        //Act
        _testContext.UserApplicationService.SignOut(id);

        //Assert
        var firstOrDefault = this._balances.FirstOrDefault(x => x.UserId == user.Id && x.MerchantId == merchantId);
        Assert.IsTrue(firstOrDefault != null && firstOrDefault.Balance == 0);
        Assert.IsNotNull(this._transactions.Where(x => x.Id == transactionId && x.Type == BonusTransactionType.EraseFunds));
    }

域单元测试

    [TestMethod]
    public void UserBonusAccount_ClearBalances_shouldClearBalancesForAllMerchants()
    {
        long userId = 1;
        long firstMerchantId = 1;
        long secondMerchantId = 2;
        User user = User.Register("111", new DateTime(2015, 01, 01, 00, 00, 01));
        Shared.Help.SetId(user, userId);
        List<BonusTransaction> transactions = new List<BonusTransaction>();
        List<BonusBalance> balances = new List<BonusBalance>();

        var userBonusAccount = UserBonusAccount.Load(transactions.AsQueryable(), balances.AsQueryable(), user);

        userBonusAccount.PayTo(new Money {TotalAmount = 100, BonusAmount = 0},
            new Outlet
            {
                BonusPercentage = 10,
                IsLoyalty = true,
                MerchantId = firstMerchantId,
                OutletId = "4512345678"
            }, "001", DateTime.Now);

        userBonusAccount.PayTo(new Money {TotalAmount = 200, BonusAmount = 0},
            new Outlet
            {
                BonusPercentage = 10,
                IsLoyalty = true,
                MerchantId = secondMerchantId,
                OutletId = "4512345679"
            }, "002", DateTime.Now);

        userBonusAccount.ClearBalances();

        Assert.IsTrue(userBonusAccount.GetBalanceAt(firstMerchantId) == 0);
        Assert.IsTrue(userBonusAccount.GetBalanceAt(secondMerchantId) == 0);
    }

如您所见，这两个测试都检查用户余额是否为0，这是域责任。因此，问题是：应用程序层单元测试应该看起来如何，应该测试什么？我读过某个地方，单元测试应该在“用于流控制的应用程序服务和用于业务规则的域模型”中进行测试。有人可以详细说明并举例说明应测试什么样的应用程序层单元测试吗？