public void Aggregate()
{
Nullable <int> n = 2;
Nullable <int> n0 = null;
Assert.Throws <ArgumentNullException>(() => NullableExtensions.Aggregate <int, int>(n, 2, null));
Assert.Equal(3, n.Aggregate(1, (sum, i) => sum + i));
Assert.Equal(1, n0.Aggregate(1, (sum, i) => sum + i));
// not called
Assert.Equal(1, n0.Aggregate(1, (_, __) => throw new InvalidOperationException("Shpuld not be called")));
}
