Mockito When().thenReturn returning an Iterator

Question

I am trying to return an iterator from when().theReturn but I keep getting this error:

org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
Itr cannot be returned by findAll()
findAll() should return List

This what I'm trying to do:

List<Client> iterList = mockClientList1.findAll();
final Iterator<Client> iter = newMockListClient.iterator();
when(iterList.iterator()).thenReturn(iter);

mockClientList1 is an object ClientList and findAll() is a method that returns a list of Client. I saw a post regarding a limitation of Mockito about stacking methods on when.thenReturn but I'm not sure if that is the reason why this is failing? Any tips would be very much appreciated.

Answer 1

If you want to do it like that, you need to provide a stub for the return value of findAll() too.

List<Client> mockList = mock(List.class)
when(mockClientList1.findAll()).thenReturn(mockList);
final Iterator<Client> iter = newMockListClient.iterator();
when(mockList.iterator()).thenReturn(iter);

But unless there's a specific reason you want to stub only the iterator, you can also return the list directly:

when(mockClientList1.findAll()).thenReturn(mockListClient);