public void Tokens_SelfNull ()
{
IEnumerable<int> s = null;
Func<int, int, int> a = (x, y) => x+y;
Func<int, Tuple<int, int>> rs = x => Tuple.Create (x, 0);
Func<int, int, bool>[] cats = new Func<int, int, bool>[]{
(p, c) => p + c < 10
};
IEnumerable<int> r = s.Tokens (0, a, rs, cats);
}