public void SelectMany_ArgumentChecking()
{
var ns = default(ISubscribable <int>);
var xs = DummySubscribable <int> .Instance;
ReactiveAssert.Throws <ArgumentNullException>(() => Subscribable.SelectMany(ns, _ => xs));
ReactiveAssert.Throws <ArgumentNullException>(() => Subscribable.SelectMany(xs, default(Func <int, ISubscribable <string> >)));
ReactiveAssert.Throws <ArgumentNullException>(() => Subscribable.SelectMany(ns, _ => xs, (x, y) => x + y));
ReactiveAssert.Throws <ArgumentNullException>(() => Subscribable.SelectMany(xs, default(Func <int, ISubscribable <string> >), (x, y) => x + y));
ReactiveAssert.Throws <ArgumentNullException>(() => Subscribable.SelectMany(xs, _ => xs, default(Func <int, int, int>)));
}