sortedTable = TreeBasedTable.create(Collections.reverseOrder(), Ordering.usingToString());
    assertThat(sortedTable.rowMap().comparator()).isEqualTo(Collections.reverseOrder());
  }

  public void testRowMapFirstKey() {
    sortedTable = create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    assertThat(sortedTable.rowMap().firstKey()).isEqualTo("bar");
  }

  public void testRowMapLastKey() {