@Test
  public void registerDropController() {
    underTest.enableDropTarget(widget);

    ArgumentCaptor<ResourceSetAvatarDropController> captor =
        ArgumentCaptor.forClass(ResourceSetAvatarDropController.class);

    verify(dragController, times(1)).registerDropController(captor.capture());

    assertEquals(widget, captor.getValue().getDropTarget());
  }
 @Test
 public void disposeRemovesDropController() {
   underTest.disableDropTarget(widget);
   verify(dragController, times(1)).unregisterDropControllerFor(eq(widget));
 }