assertThat(onlyPresent).containsExactly("a", "c").inOrder();
    assertThat(onlyPresent).containsExactly("a", "c").inOrder();
  }

  public void testPresentInstances_wildcards() {
    List<Optional<? extends Number>> optionals =
        ImmutableList.<Optional<? extends Number>>of(Optional.<Double>absent(), Optional.of(2));