@Test
    public void testSingle () {
	Rectangle2D rx = new Rectangle2D.Double (0, 0, 1, 1);
	tree.load (Collections.singletonList (rx));
	MBR mbr = tree.getMBR ();
	assertEquals ("odd min for mbr", 0, mbr.getMinX (), 0);
	assertEquals ("odd min for mbr", 0, mbr.getMinY (), 0);
	assertEquals ("odd max for mbr", 1, mbr.getMaxX (), 0);
	assertEquals ("odd max for mbr", 1, mbr.getMaxY (), 0);
	assertEquals ("height of tree with one entry", 1, tree.getHeight ());
	int count = 0;
	for (Rectangle2D r : tree.find (0, 0, 1, 1)) {
	    assertEquals ("odd rectangle returned", rx, r);
	    count++;
	}
	assertEquals ("odd number of rectangles returned", 1, count);

	for (Rectangle2D r : tree.find (5, 5, 6, 7))
	    fail ("should not find any rectangle");

	for (Rectangle2D r : tree.find (-5, -5, -2, -4))
	    fail ("should not find any rectangle");
    }