Mockito不断返回空列表

Question

I'm working on unit testing a method in Mockito and mockito keeps sending an empty zero size list even when I have initialized the list that is to be returned.

This is the code to be tested. Note that nonCashIncludedPaymentPlanActive is always true ( Mocked ).

    List<DebtAccountTransaction> debtAccountTransactionList = null;

    boolean nonCashIncludedPaymentPlanActive = balancingPlanService.checkNonCashIncludedPaymentPlanParameter(debtAccountId);


    if (nonCashIncludedPaymentPlanActive) {
        debtAccountTransactionList = debtAccountTransactionDao
                .getDebtAccountTransactionListByDebtAccountIdListWithCN(baseDebtIdAccountList, null);
    } 
    if (debtAccountTransactionList.isEmpty()) {
        throw new SfcException("DISPLAY.PAYMENT_PLAN_WITH_NO_BALANCE_SERVICE_FILE_CLOSED");
    }

This the statement that keeps returning a List that I have mocked in mockito and added an item to it and here it returns an emptylist.

debtAccountTransactionList = debtAccountTransactionDao
                .getDebtAccountTransactionListByDebtAccountIdListWithCN(baseDebtIdAccountList, null);

which then ofcourse gets caught by this line

if (debtAccountTransactionList.isEmpty()) {
        throw new SfcException("DISPLAY.PAYMENT_PLAN_WITH_NO_BALANCE_SERVICE_FILE_CLOSED");
    }

Thus inorder to avoid this path of execution I have done the following in Mockito:

when(debtAccountTransactionDao.getDebtAccountTransactionListByDebtAccountIdListWithCN(baseDebtIdAccountList, null)).thenReturn(
            debtAccountTransactionList);

and declaration of debtAccountTransactionList is :

DebtAccountTransaction debtAccountTransaction = spy(DebtAccountTransaction.class);
    debtAccountTransaction.setId(2L);


    List<DebtAccountTransaction> debtAccountTransactionList = new ArrayList<DebtAccountTransaction>();
    debtAccountTransactionList.add(debtAccountTransaction);

I tried mocking a List, tried different argument captors but nothing seems to work. When I debug it, Mockito does fill up the debtAccountTransactionList but with an empty List, thus it fails.

Any help with how I can make sure that Mockito sends a Non-Empty Non-Zero List so that it can bypass the isEmpty() check.

Answer 1

A good rule of thumb in writing tests, especially with a mocking library like Mockito: Don't confuse stubbing with verification. Stubbing ( when ) is about getting your system under test (SUT) into the desired state, not about asserting anything about how the SUT behaves.

In Mockito, the way to make assertions about how the SUT behaves is after the SUT runs, using verify calls. If you don't have any verify calls, you're not actually asserting anything, and your SUT can misbehave without your test catching it, which is obviously a bad thing.

As a result, it's usually best to make your matchers for stubbing ( when ) as broad as possible, since the goal of stubbing is just to make sure you fall into the right test case. For example, you can and often should use matchers like any() in your when() call. If you did that, you would sidestep the issue you're having here.

If you want to make assertions about the values that the SUT actually used as arguments, do that with verify , or possibly by capturing the value and making additional assertions about it directly.

Answer 2

Did you put in any place of the code something like:

debtAccountTransactionDao = Mockito.mock(NameOfTheClassOfThisDebtAccountObject.class);

?

You should put something like this before calling the method getDebtAccountTransactionListByDebtAccountIdListWithCN , so it knows it should use the mocked behavior, not the normal behavior of the method (that could be return an empty list).

Answer 3

The problem is the mock creation/behavior registration. This doesn't match what you put into the method and hence returns to the default behavior of returning an empty list.

as pointed out by M. Deinum

Thus there was a problem in acceptance of the argument by Mockito and it would ignore my stubbing and then return an empty list by default.

I fixed it by making sure the object that is baseDebtIdAccountList passed to the function when(debtAccountTransactionDao.getDebtAccountTransactionListByDebtAccountIdListWithCN(baseDebtIdAccountList, null)).thenReturn( debtAccountTransactionList) is exactly the same in the rest of the code. Thus there was a mismatch in the arguments and Mockito used the default way of using an empty list.