.inOrder();
  }

  public void testToMap_nullKey() {
    assertThrows(
        NullPointerException.class, () -> fluent(1, null, 2).toMap(Functions.constant("foo")));
  }

  public void testToMap_nullValue() {
    assertThrows(NullPointerException.class, () -> fluent(1, 2, 3).toMap(Functions.constant(null)));
  }

  public void testIndex() {
    ImmutableListMultimap<Integer, String> expected =