public void ExpiryEndOfWeekTests()
        {
            var endOfWeekList = new List <DateTime>();

            var current = new DateTime(2019, 1, 1);
            var end     = new DateTime(2020, 1, 1);

            while (current < end)
            {
                var endOfWeek = Expiry.EndOfWeek(current);
                endOfWeekList.Add(endOfWeek);
                Assert.AreEqual(DayOfWeek.Monday, endOfWeek.DayOfWeek);
                Assert.Greater(endOfWeek, current);
                current = current.AddDays(1);
            }

            var actual = endOfWeekList.Distinct().Count();

            Assert.AreEqual(53, actual);
        }