assertThrows(IllegalStateException.class, () -> builder.concurrencyLevel(16));
  }

  @GwtIncompatible // CacheTesting
  public void testConcurrencyLevel_small() {
    LoadingCache<?, ?> cache =
        CacheBuilder.newBuilder().concurrencyLevel(1).build(identityLoader());
    LocalCache<?, ?> map = CacheTesting.toLocalCache(cache);