public void ToWeekdayForAWeekdayShouldReturnTheSameDay()
        {
            var dt = new DateTime(2015, 11, 09);
            var res = dt.ToWeekday();

            Assert.AreEqual(dt, res);
        }
        public void ToWeekdayForASundayShouldReturnTheFollowingMonday()
        {
            var dt = new DateTime(2015, 11, 08);
            var result = dt.ToWeekday();

            Assert.AreEqual(new DateTime(2015, 11, 09), result);
        }