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));
    assertThat(cache.size()).isEqualTo(1);
  }