模拟DAO类及其中的方法

Question

I am trying to mock a DAO class that has a method which returns a list of a specific class.

private List<SpecificClass> getInfo(){

List<SpecificClass> returnInformation = dao.list(ParamOne, Param Two, SpecificClass.class);
}

The dao mentioned in the above method refers to another class.

I begin by mocking that DAO class.

Mockito.mock(TheDaoClass.class);

and creating a mocked list

private @Mock List<SpecificClass> returnedList = new ArrayList<SpecificClass>();

Then I make call to that method

dao.list(ParamOne, Param Two, SpecificClass.class);

and specify what needs to be done when it is called

when(dao.list(ParameterOne, anyString(), SpecificClass.class)).thenReturn(returnedList);

When I do the above I get a null pointer exception. There can be two causes:

I understand the list is empty but all it is supposed is hold SpecificClass's five values but that shouldn't throw an error at this point.

I think object dao is not getting mocked properly. I am only mocking the whole class Mockito.mock(TheDaoClass.class) in order to mock any object asociated with that class. I think that it is not achieving the objective. how do I go about solving this problem? Any help is appreciated. Thanks.

Answer 1

Make your mocked DAO object a property of your test class like so:

@Mock
private TheDaoClass mockDaoClass;

Then, in your setUp() method at the beginning of your test class call initMocks :

@BeforeClass
public void setUp() {
    MockitoAnnotations.initMocks(this);
}

This should prevent the NullPointer .

Additionally, I recommend that rather than mock the List object (if you are mocking any Java library data type you are probably doing it wrong), you should create a list and populate it.

List<SpecificClass> list = new ArrayList<SpecificClass>();
list.add(new SpecificClass());

Then return the list from the mocked method.

when(mockDaoClass.list(anyString(), anyString(), SpecificClass.class)).thenReturn(list);