@Override
  public Iterator<WorkerInfo> iterator() {
    return Iterators.unmodifiableIterator(mWorkers.values().iterator());
  }
@Test
  public void immutableIterator() {
    WorkerClusterView view = new WorkerClusterView(ImmutableList.of(
        new WorkerInfo().setIdentity(WorkerIdentityTestUtils.randomLegacyId())));
    Iterator<WorkerInfo> iter = view.iterator();
    assertTrue(iter.hasNext());
    while (iter.hasNext()) {
      iter.next();
      assertThrows(UnsupportedOperationException.class, iter::remove);
    }
  }