svoid test_pixelSpiral() {

  int maxW = 10, maxH = maxW;

  for (int w = 1; w <= maxW; w++)

    for (int h = 1; h <= maxH; h++) {

      print("Testing " + w + "*" + h);

      Set<Pt> allPoints = asSet(allPointsInRect(w, h));

      for x to w: for y to h: {

        print("  " + x + "/" + y);

        L<Pt> l = asList(pixelSpiral(x, y, w, h));

        assertEquals(l(l), w*h);

        assertEquals(asSet(l), allPoints);

        assertEquals(first(l), pt(x, y));

        // We trust the remaining points are in the correct order

      }

    }

  print("pixelSpiral (probably) OK up to " + maxW + "*" + maxH);

}