assertThrows(
            IllegalArgumentException.class, () -> range.intersection(Range.closed(10, 12)));
    assertThat(expected).hasMessageThat().contains("connected");
  }

  public void testGap_overlapping() {
    Range<Integer> range = Range.closedOpen(3, 5);

    assertThrows(IllegalArgumentException.class, () -> range.gap(Range.closed(4, 6)));