How to create a mock of list of a custom data type in Mockito?

Question

I have a class User with the following definition :

class User {

  Integer id;
  String name;
  String addr;

  //getters and setters

}

Now while testing a function, I am required to return a list of mocked Users for a stub, something like:

Mockito.when(userService.getListOfUsers()).thenReturn(mockList);

Now this mockList could be created as the following :

List mockList = Mockito.mock(ArrayList.class);

But this mockList could be a list of anything. I won't be able to ensure its type. Is there a way to create list of :

List<User> mockListForUser = Mockito.mock(?);

Answer 1

You probably want to populate a normal list with your mocked objects. E.g.

List<User> mockList = new ArrayList<>();

User mockUser1 = Mockito.mock(User.class);
// ...    

mockList.add(mockUser1);
// etc.

Note that by default, Mockito returns an empty collection for any mocked methods that returns a collection. So if you just want to return an empty list, Mockito will already do that for you.

Answer 2

Use the @Mock annotation in your test since Mockito can use type reflection:

@Mock
private ArrayList<User> mockArrayList;