for (int i = 0; i < size; i++) {
      referenceMap.put(i, null);
    }
    assertWithMessage("table size after adding " + size + " elements")
        .that(initialBuckets)
        .isAtMost(bucketsOf(referenceMap));
  }

  @J2ktIncompatible
  @GwtIncompatible // reflection
  private static int bucketsOf(HashMap<?, ?> hashMap) throws Exception {