public static void IntListListCreation(List <int>[] xs)
        {
            var expected = xs.ToList();
            var cache    = new ListCache(1);
            var actual   = (FuncList <List <int> >)cache.RetrieveOrCacheCreate(typeof(List <int>), xs.Cast <object>());

            Assert.Equal(expected, actual);
        }
        public static void StringListCreation(string[] xs)
        {
            var expected = xs.ToList();
            var cache    = new ListCache(1);
            var actual   = (FuncList <string>)cache.RetrieveOrCacheCreate(typeof(string), xs.Cast <object>());

            Assert.Equal(expected, actual);
        }