public void testEquals() {
   LongArrayAndSize l1 = new LongArrayAndSize(10);
   LongArrayAndSize l1a = new LongArrayAndSize(10);
   LongArrayAndSize l2 = new LongArrayAndSize(10);
   for (long i = 0; i < 8; i++) {
     l1.add(i);
     l1a.add(i);
     l2.add(i + 1);
   }
   l1.data[9] = 123; // should be
   l1a.data[9] = 234; // irrelevant
   assertEquals(l1, l1a);
   assertFalse(l1.equals(l2));
   l1.add(234);
   assertFalse(l1.equals(l1a));
 }