public void LoadHolidays_ReturnsTrue_ForDateAddedAsListItem() { //Arrange HolidaysManager manager = new HolidaysManager(); List<DateTime> holidays = new List<DateTime>(); holidays.Add(new DateTime(2017, 5, 1)); holidays.Add(new DateTime(2017, 5, 3)); holidays.Add(new DateTime(2017, 11, 11)); DateTime checkedDate = new DateTime(2017, 5, 2); //Act manager.LoadHolidays(holidays); //Assert bool isHoliday = manager.IsHoliday(checkedDate); Assert.IsFalse(isHoliday); }