it.assertValue(1, "a2")
    }
    assertThat(iterator.hasNext()).isTrue()
    iterator.next().use {
      assertThat(it.key()).isEqualTo("b")
      it.assertValue(0, "b1")
      it.assertValue(1, "b2")
    }
    assertThat(iterator.hasNext()).isTrue()
    iterator.next().use {
      assertThat(it.key()).isEqualTo("c")
      it.assertValue(0, "c1")
      it.assertValue(1, "c2")
    }

  //    (hypothetical) unsafe read by our caller. Note: adding 'volatile' does not fix this issue,
  //    it would just add an edge such that if done() observed non-null, then it would also
  //    definitely observe all earlier writes, but we still have no guarantee that done() would see
  //    the initial write (just stronger guarantees if it does).
  //
  // See: http://cs.oswego.edu/pipermail/concurrency-interest/2015-January/013800.html

 * API</h2>
 *
 * <p>The successor to Guava's caching API is <a
 * href="https://github.com/ben-manes/caffeine/wiki">Caffeine</a>. Its API is designed to make it a
 * nearly drop-in replacement. Note that it is not available for Android or GWT/J2CL and that it may
 * have <a href="https://github.com/ben-manes/caffeine/wiki/Guava">different (usually better)

    This simple option dramatically changes the behavior of the request body and of the entire
    call.

    The `RequestBody.writeTo()` method may now retain a reference to the provided sink and
    hand it off to another thread to write to it after `writeTo` returns.

    The `EventListener` may now see requests and responses interleaved in ways not previously
    permitted. For example, a listener may receive `responseHeadersStart()` followed by

    // Write the mocking script.
    peer.sendFrame().settings(Settings())
    peer.acceptFrame() // ACK
    peer.sendFrame().ping(false, 2, 3)
    peer.acceptFrame() // PING
    peer.play()

    // Play it back.
    connect(peer)

    // Verify the peer received what was expected.
    val ping = peer.takeFrame()
    assertThat(ping.type).isEqualTo(Http2.TYPE_PING)
    assertThat(ping.streamId).isEqualTo(0)

 * /static/images/../../../../../etc/passwd
 * /etc/passwd
 * ```
 *
 * ### If it works on the web, it should work in your application
 *
 * The `java.net.URI` class is strict around what URLs it accepts. It rejects URLs like
 * `http://example.com/abc|def` because the `|` character is unsupported. This class is more
 * forgiving: it will automatically percent-encode the `|'` yielding `http://example.com/abc%7Cdef`.

 *
 * <p>A step can be the input to at most one derived step. Once you transform its value, catch its
 * exception, or combine it with others, you cannot do anything else with it, including declare it
 * to be the last step of the pipeline.
 *
 * <h4>Transforming</h4>
 *
 * To derive the next step by asynchronously applying a function to an input step's value, call

 * API</h2>
 *
 * <p>The successor to Guava's caching API is <a
 * href="https://github.com/ben-manes/caffeine/wiki">Caffeine</a>. Its API is designed to make it a
 * nearly drop-in replacement. Note that it is not available for Android or GWT/J2CL and that it may
 * have <a href="https://github.com/ben-manes/caffeine/wiki/Guava">different (usually better)

    return set;
  }

  /**
   * Creates a {@code LinkedHashSet} instance, with a high enough "initial capacity" that it
   * <i>should</i> hold {@code expectedSize} elements without growth. This behavior cannot be
   * broadly guaranteed, but it is observed to be true for OpenJDK 1.7. It also can't be guaranteed
   * that the method isn't inadvertently <i>oversizing</i> the returned set.
   *

  val connectionPool: ConnectionPool =
    builder.connectionPool ?: ConnectionPool().also {
      // Cache the pool in the builder so that it will be shared with other clients
      builder.connectionPool = it
    }

  constructor() : this(Builder())

  init {
    if (connectionSpecs.none { it.isTls }) {
      this.sslSocketFactoryOrNull = null
      this.certificateChainCleaner = null
      this.x509TrustManager = null