public void testToSortedSet() {
    assertThat(fluent(1, 4, 2, 3).toSortedSet(Ordering.<Integer>natural().reverse()))
        .containsExactly(4, 3, 2, 1)
        .inOrder();
  }

  public void testToSortedSet_removeDuplicates() {
    assertThat(fluent(1, 4, 1, 3).toSortedSet(Ordering.<Integer>natural().reverse()))
        .containsExactly(4, 3, 1)
        .inOrder();
  }

  public void testToMultiset() {