}

  public void testOpen_invalid() {
    assertThrows(IllegalArgumentException.class, () -> Range.open(4, 3));
    assertThrows(IllegalArgumentException.class, () -> Range.open(3, 3));
  }

  public void testClosed() {
    Range<Integer> range = Range.closed(5, 7);
    checkContains(range);
    assertTrue(range.hasLowerBound());
    assertEquals(5, (int) range.lowerEndpoint());
    assertEquals(CLOSED, range.lowerBoundType());