@Test
 public void testGetParent() {
   System.out.println("testGetParent");
   for (Category root : serviceStub.getRootCategories()) {
     assertNull(container.getParent(root.getId()));
     for (Category child : serviceStub.getChildren(root)) {
       assertEquals(root.getId(), container.getParent(child.getId()));
     }
   }
 }