public void test_plus_longPeriodUnit_negativeDays() {

    LocalDateTime t = this.TEST_2007_07_15_12_30_40_987654321.plus(-25, ChronoUnit.DAYS);
    assertEquals(t, LocalDateTime.of(2007, 6, 20, 12, 30, 40, 987654321));
  }

  @Test(expectedExceptions = NullPointerException.class, groups = { "tck" }