svoid test_HashedImage2B() {
  var img1 = randomImage(10);
  var himg1 = new HashedImage2B(img1);
  var himg2 = new HashedImage2B(img1);
  assertEquals(himg1.hashCode(), himg2.hashCode());
  assertEquals(himg1.hash(), himg2.hash());
  assertEquals(himg1, himg2);
  
  var img3 = randomImage(10);
  var himg3 = new HashedImage2B(img3);
  assertNotEquals(himg1.hashCode(), himg3.hashCode());
  assertNotEquals(himg1.hash(), himg3.hash());
  assertNotEquals(himg1, himg3);
}

Began life as a copy of #1034844