List<Restriction> restrictions = new ArrayList<>(r1.size() + r2.size());
        Iterator<Restriction> i1 = r1.iterator();
        Iterator<Restriction> i2 = r2.iterator();
        Restriction res1 = i1.next();
        Restriction res2 = i2.next();

        boolean done = false;
        while (!done) {
            if (res1.getLowerBound() == null
                    || res2.getUpperBound() == null

    // Test & Verify
    Iterator<String> i1 = Iterables.consumingIterable(list).iterator();
    Iterator<String> i2 = Iterables.consumingIterable(list).iterator();

    i1.next();
    assertThrows(ConcurrentModificationException.class, () -> i2.next());
  }

  public void testConsumingIterable_queue_iterator() {
    List<Integer> items = ImmutableList.of(4, 8, 15, 16, 23, 42);

    // Test & Verify
    Iterator<String> i1 = Iterables.consumingIterable(list).iterator();
    Iterator<String> i2 = Iterables.consumingIterable(list).iterator();

    i1.next();
    assertThrows(ConcurrentModificationException.class, () -> i2.next());
  }

  public void testConsumingIterable_queue_iterator() {
    List<Integer> items = ImmutableList.of(4, 8, 15, 16, 23, 42);