@Test
public void calendarDayToYearMonth() {

  CalendarDay calendarDay = CalendarDay.from(2016, 10, 15);
  YearMonth expectedYearMonth = YearMonth.of(2016, 11);
  YearMonth actuaYearMonth = DateHelper.calendarDayToYearMonth(calendarDay);
  assertEquals(expectedYearMonth, actuaYearMonth);
}