}

  public void testCopyInto_list() {
    assertThat(fluent(1, 3, 5).copyInto(Lists.newArrayList(1, 2)))
        .containsExactly(1, 2, 1, 3, 5)
        .inOrder();
  }

  public void testCopyInto_set() {
    assertThat(fluent(1, 3, 5).copyInto(newHashSet(1, 2))).containsExactly(1, 2, 3, 5);
  }

  public void testCopyInto_setAllDuplicates() {