svoid test_ImageSimilarityAtScale_equalImages() {
  var img = randomImage(50, 20);
  var ii = IntegralImage(img);
  ImageSimilarityAtScale algo = new(ii, ii, 4);
  algo.run();
  int i = 1;
  for (i = 1; i <= 254; i++) {
    assertTrue(str(i), algo.step());
    assertEquals(0.0, algo.diff());
  }
  assertFalse(str(i), algo.step());
}

Began life as a copy of #1032164