public void ContainsFlagEnumTest()
        {
            var week = WeekEnum.Monday;

            FlagEnums.Contains(week, WeekEnum.Monday).ShouldBeTrue();
            FlagEnums.Contains(week, WeekEnum.Tuesday).ShouldBeFalse();

            FlagEnums.Add(ref week, WeekEnum.Tuesday, WeekEnum.Wednesday);

            FlagEnums.Contains(week, WeekEnum.Monday).ShouldBeTrue();
            FlagEnums.Contains(week, WeekEnum.Tuesday).ShouldBeTrue();
        }