public void GetLastDayOfWeekForATuesdayShouldReturnTheNextSundayForFirstDayOfWeekBeingMonday() { //Setup var workingDate = new DateTime(2014, 7, 8); //A Tuesday //Exercise var lastDayOfWeek = DayHelper.GetLastDayOfWeek(workingDate, DayOfWeek.Monday); //Verify Assert.AreEqual(DayOfWeek.Tuesday, workingDate.DayOfWeek); Assert.AreEqual(new DateTime(2014, 7, 13), lastDayOfWeek); }