@Override
 @Test
 public void removeEdge_oneOfMany() {
   expectedException.expect(UnsupportedOperationException.class);
   super.removeEdge_oneOfMany();
 }
 @Override
 @Test
 public void removeEdge_invalidArgument() {
   expectedException.expect(UnsupportedOperationException.class);
   super.removeEdge_invalidArgument();
 }
 @Override
 @Test
 public void removeEdge_existingEdge() {
   expectedException.expect(UnsupportedOperationException.class);
   super.removeEdge_existingEdge();
 }