private static void assertWontGrow(
      int size,
      HashMap<Object, Object> referenceMap,
      HashMap<Object, Object> map1,
      HashMap<Object, Object> map2)
      throws Exception {
    // Only start measuring table size after the first element inserted, to
    // deal with empty-map optimization.
    map1.put(0, null);

    int initialBuckets = bucketsOf(map1);

    for (int i = 1; i < size; i++) {