fun cache(cache: Cache?) =
      apply {
        this.cache = cache
      }

    internal fun taskRunner(taskRunner: TaskRunner) =
      apply {
        this.taskRunner = taskRunner
      }

    /**
     * Sets the DNS service used to lookup IP addresses for hostnames.
     *
     * If unset, the [system-wide default][Dns.SYSTEM] DNS will be used.

  private val taskRunner = taskFaker.taskRunner
  private lateinit var cache: DiskLruCache
  private val toClose = ArrayDeque<DiskLruCache>()

  private fun createNewCache() {
    createNewCacheWithSize(Int.MAX_VALUE)
  }

  private fun createNewCacheWithSize(maxSize: Int) {
    cache =
      DiskLruCache(filesystem, cacheDir, appVersion, 2, maxSize.toLong(), taskRunner).also {
        toClose.add(it)
      }

    peer.acceptFrame() // SYN_STREAM.
    peer.play()
    val taskRunner = taskFaker.taskRunner
    val connection =
      Http2Connection
        .Builder(true, taskRunner)
        .socket(peer.openSocket().asBufferedSocket(), "peer")
        .pushObserver(IGNORE)
        .build()
    connection.start(sendConnectionPreface = false)
    val queues = taskRunner.activeQueues()
    assertThat(queues).hasSize(1)
  }