public void Retry2()
        {
            var ex = new InvalidOperationException("Bang!");

            var xs = new[] { 1, 2, 3 }.ToAsyncEnumerable().Concat(AsyncEnumerable.Throw<int>(ex));

            var res = xs.Retry();

            var e = res.GetEnumerator();
            HasNext(e, 1);
            HasNext(e, 2);
            HasNext(e, 3);
            HasNext(e, 1);
            HasNext(e, 2);
            HasNext(e, 3);
            HasNext(e, 1);
            HasNext(e, 2);
            HasNext(e, 3);
        }
        public void Retry1()
        {
            var xs = new[] { 1, 2, 3 }.ToAsyncEnumerable();

            var res = xs.Retry();

            var e = res.GetEnumerator();
            HasNext(e, 1);
            HasNext(e, 2);
            HasNext(e, 3);
            NoNext(e);
        }