assertThat(elementSet).containsExactly("a", "c", "f").inOrder();
    assertThat(subset).containsExactly("c");
    assertEquals(5, ms.size());
  }

  public void testElementSetSubsetClear() {
    TreeMultiset<String> ms = TreeMultiset.create();
    ms.add("a", 1);
    ms.add("b", 3);
    ms.add("c", 2);
    ms.add("d", 1);
    ms.add("e", 3);
    ms.add("f", 2);