public void TestFilterNotNull()
{
var e = new FirableEvent<string>();
var o = new List<string>();
var l = e.Filter(x => x != null).Subscribe(o.Add);
e.Fire("tomato");
e.Fire(null);
e.Fire("peach");
l.Dispose();
AssertArraysEqual(Arrays<string>.AsList("tomato", "peach"), o);
}