public void ExpiryEndOfMonthTests() { var endOfMonthList = new List <DateTime>(); var current = new DateTime(2019, 1, 1); var end = new DateTime(2020, 1, 1); while (current < end) { var endOfMonth = Expiry.EndOfMonth(current); endOfMonthList.Add(endOfMonth); Assert.AreEqual(1, endOfMonth.Day); Assert.Greater(endOfMonth, current); current = current.AddDays(1); } var actual = endOfMonthList.Distinct().Count(); Assert.AreEqual(12, actual); }