static void Main()
{
var calendarUtils = new CalendarUtils();
var startDate = new DateTime(1901, 1, 1);
var endDate = new DateTime(2000, 12, 31);
var sundayOnFirstOfMonth = calendarUtils.GetSundaysThatAreOnTheFirstDayOfMonth(startDate, endDate);
Console.WriteLine($"Number of Sundays on the first of the month during the 20th century: {sundayOnFirstOfMonth.Count}");
Console.ReadKey();
}
public void WhenGettingSundaysThatAreOnFirstDayOfMonth_ThenGetCorrectAmount()
{
// Arrange
var startDate = new DateTime(2019, 1, 1);
var endDate = new DateTime(2019, 12, 31);
// Act
var result = _calendarUtils.GetSundaysThatAreOnTheFirstDayOfMonth(startDate, endDate);
// Assert
Assert.AreEqual(2, result.Count);
}