svoid test_RegionBorder_innerPoints() {
  //set flag RegionBorder_innerPoints_debug.
  //set flag FastRegions_debug.
  BWImage img = bwImageFromString([[
    ______
    ______
    __xx__
    __xx__
    ______
    ______
  ]]);
  FastRegions_BWImage regions = new(img);
  regions.run();
  for (int i = 1; i <= regions.nRegions(); i++)
    print("Region " + i + ": " + map ptWithSlashes(regions.regionPixels(i)));
  /*for (int i = 1; i <= regions.nRegions(); i++)
    print("Region " + i + ": " + map ptWithSlashes(regionBorder_innerPoints(regions, i)));*/
  
  for (int i = 1; i <= regions.nRegions(); i++)
    new RegionBorder_innerPoints(regions, i).runAndPrint();
}

Began life as a copy of #1033943