assertThat(fluent(1, 2, 1, 2).toSet()).containsExactly(1, 2).inOrder();
  }

  public void testToSet_empty() {
    assertTrue(fluent().toSet().isEmpty());
  }

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

  public void testToSortedSet_removeDuplicates() {