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);
}