public void BlackQuadEnumeration()
{
var qt = new RegionQuadtree <int>(3);
qt.Set(1);
Assert.Equal(1, qt.Count());
Assert.Equal(1, qt.ElementAt(0));
qt.Set(new Point2i(0, 0), 2);
Assert.True(qt.Contains(2));
Assert.Equal(10, qt.Count());
Assert.Equal(9, qt.Count((i) => i == 1));
}