Unit Test for a Function that determines the date after a change in days. For instance 12 days from today or 14 days from now

rollback_date.java

@Test
    public void rollTimeByDaysTest(){
        //==================================
        //TEST CASE 1
        //==================================
        System.out.println("Test case I");
        DateTime dateTime = new DateTime(2020,12,14,0,0);
        DateTime newDate = DateTimeUtils.rollBackByDayOfMonth(dateTime, 7);
        System.out.println(" newDate " + DateTimeUtils.convertDateToString(newDate));
        Assertions.assertEquals(8,newDate.dayOfMonth().get());
        Assertions.assertEquals(12, newDate.monthOfYear().get());

        //==================================
        //TEST CASE 2
        //==================================
        System.out.println("Test case II");
        DateTime dateTime2 = new DateTime(2020,12,2,0,0);
        System.out.println("Date Time 2 " + DateTimeUtils.convertDateToString(dateTime2));
        DateTime newDate2 = DateTimeUtils.rollBackByDayOfMonth(dateTime2, 7);
        System.out.println(" newDate " + DateTimeUtils.convertDateToString(newDate2));
        Assertions.assertEquals(26,newDate2.dayOfMonth().get());
        Assertions.assertEquals(11, newDate2.monthOfYear().get());

        //==================================
        //TEST CASE 3
        //==================================
        System.out.println("Test case III");
        DateTime dateTime3 = new DateTime(2020,12,7,0,0);
        DateTime newDate3 = DateTimeUtils.rollBackByDayOfMonth(dateTime3, 7);
        System.out.println(" newDate " + DateTimeUtils.convertDateToString(newDate3));
        Assertions.assertEquals(1,newDate3.dayOfMonth().get());
        Assertions.assertEquals(12, newDate3.monthOfYear().get());
    }