Unit testing Collection in Java

I have a unit test that will allow me to iterate through a Collection object containing a list of vehicle. Upon each iteration, I want to check to see if the vehicle is an instance of automobile. So my code looks a bit like this:

public class VehicleChecker {
    protected boolean checkVehicles(Garage garage) {
        for (Vehicle vehicle : garage.getVehicles() {
            if (vehicle instanceof Automobile) return true;
        }
    }
}

So I wrote my code accordingly:

@Mock private Garage mockGarage;
@Mock private VehicleCollection mockVehicleCollection;
@Mock private VehicleCollectionIterator mockVehicleCollectionIterator;
@Mock private Vehicle mockVehicle;

@Test
public void testCheckVehicles() {

    VehicleChecker testObject = new vehicleChecker();

    when(mockGarage.getVehicles()).thenReturn(mockVehicleCollection);
    when(mockVehicleCollection.iterator()).thenReturn(mockVehicleCollectionIterator);
    when(mockVehicleCollectionIterator.hasNext()).thenReturn(true).thenReturn(false);
    when(mockVehicleCollectionIterator.next()).thenReturn(mockVehicle);

    boolean result = testObject.checkVehicles(mockGarage);

    verify(mockGarage).getVehicles();
    assertEquals(true, result);
}

The problem occurs with the verify statement. Based on how it was written, the test should pass. When I step through the code, however, I the code just skips the for loop entirely. Why is that? Is there a difference in the way one iterates through a Collection as opposed to an ArrayList? If so, how do I properly mock that interaction?