super.setUp();
    this.cache =
        CacheBuilder.newBuilder()
            .expireAfterAccess(500000, MILLISECONDS)
            .maximumSize(count)
            .build();
  }

  public void testComputeIfAbsent() {
    // simultaneous insertion for same key, expect 1 winner
    doParallelCacheOp(
        count,
        n -> {
          cache.asMap().computeIfAbsent(key, k -> "value" + n);
        });