def METHOD_NAME(self, holiday_name):
    days_delta = 0 if holiday_name == "Memorial Day" else 1
    # Postponed
    official_holiday = date(2017, 4, 30) + td(days=days_delta)
    observed_holiday = official_holiday + td(days=+1)
    self.assertNotIn(holiday_name, self.holidays.get(official_holiday, ""))
    self.assertHoliday(observed_holiday)
    self.assertHolidayName(f"{holiday_name} (Observed)", observed_holiday)
    # Earlier
    official_holiday = date(2018, 4, 19) + td(days=days_delta)
    observed_holiday = official_holiday + td(days=-1)
    self.assertHoliday(observed_holiday)
    self.assertNotIn(holiday_name, self.holidays.get(official_holiday, ""))
    self.assertHolidayName(f"{holiday_name} (Observed)", observed_holiday)
    # On time
    official_holiday = date(2020, 4, 28) + td(days=days_delta)
    self.assertHoliday(observed_holiday)
    self.assertHolidayName(holiday_name, official_holiday)
    self.assertNoHolidayName(f"{holiday_name} (Observed)", 2020)