)

    client =
      clientTestRule
        .newClientBuilder()
        .eventListenerFactory(clientTestRule.wrap(eventRecorder))
        .connectTimeout(60, TimeUnit.SECONDS) // Deliberately exacerbate slow fallbacks.
        .dns { dnsResults }
        .fastFallback(true)
        .build()
    url =
      serverIpv4
        .url("/")
        .newBuilder()
        .host("localhost")
        .build()
  }

  companion object {
    /**
     * A network that resolves only one IP address per host. Use this when testing route selection
     * fallbacks to prevent the host machine's various IP addresses from interfering.
     */
    private val SINGLE_INET_ADDRESS_DNS =
      Dns { hostname ->
        val addresses = Dns.SYSTEM.lookup(hostname)

            </signature>
            <ignores>
              <!-- Unsafe isn't part of the documented Android API, but it is available.
                   And in cases where it's not, we have fallbacks (except maybe Striped64 (b/307807965)?). -->
              <ignore>sun.misc.Unsafe</ignore>
            </ignores>
          </configuration>
          <executions>
            <execution>

   * java.util.concurrent.CompletableFuture#thenAcceptAsync}.
   *
   * @param callback The callback to invoke when this {@code Future} is completed.
   * @param executor The executor to run {@code callback} when the future completes.
   */
  public final void addCallback(FutureCallback<? super V> callback, Executor executor) {
    Futures.addCallback(this, callback, executor);
  }

                Request
                  .Builder()
                  .url(server.url("/a"))
                  .build()
              try {
                val callbackA = RecordingCallback()
                client.newCall(requestA).enqueue(callbackA)
                callbackA.await(requestA.url).assertBody("a")
              } catch (e: Exception) {
                throw RuntimeException(e)
              }
            }

        NameCallback nc = new NameCallback("user:");
        PasswordCallback pc = new PasswordCallback("pass:", false);

        // Exercise callback handler with both callbacks supplied
        Callback[] cbs = new Callback[] { nc, pc };
        auth.handle(cbs);

        // Name should be formatted as username@domain
        assertEquals("user@DOM", nc.getName());
        // Password should be set

 *  **TLS configuration updated.** OkHttp now explicitly enables TLSv1.2,
    TLSv1.1 and TLSv1.0 where they are supported. It will continue to perform
    only one fallback, to SSLv3. Applications can now configure this with the
    `ConnectionSpec` class.

    To disable TLS fallback:

    ```java
    client.setConnectionSpecs(Arrays.asList(
        ConnectionSpec.MODERN_TLS, ConnectionSpec.CLEARTEXT));
    ```

   * across calls to multiple listeners. Specifically, a given listener will have its callbacks
   * invoked in the same order as the underlying service enters those states. Additionally, at most
   * one of the listener's callbacks will execute at once. However, multiple listeners' callbacks
   * may execute concurrently, and listeners may execute in an order different from the one in which
   * they were registered.

   * across calls to multiple listeners. Specifically, a given listener will have its callbacks
   * invoked in the same order as the underlying service enters those states. Additionally, at most
   * one of the listener's callbacks will execute at once. However, multiple listeners' callbacks
   * may execute concurrently, and listeners may execute in an order different from the one in which
   * they were registered.

   * across calls to multiple listeners. Specifically, a given listener will have its callbacks
   * invoked in the same order as the underlying service enters those states. Additionally, at most
   * one of the listener's callbacks will execute at once. However, multiple listeners' callbacks
   * may execute concurrently, and listeners may execute in an order different from the one in which
   * they were registered.