}

  public void testFirst_null() {
    List<String> list = Lists.newArrayList(null, "a", "b");
    assertThrows(NullPointerException.class, () -> FluentIterable.from(list).first());
  }

  public void testFirst_emptyList() {
    List<String> list = emptyList();
    assertThat(FluentIterable.from(list).first()).isAbsent();
  }

  public void testFirst_sortedSet() {