public void GetYearDays()
        {
            var vacation = new Vacation()
            {
                Start = new DateTime(2018, 1, 1),
                End   = new DateTime(2019, 1, 1),
            };

            Assert.Equal(1, vacation.GetDaysForYear(2019));
            Assert.Equal(365, vacation.GetDaysForYear(2018));
        }