could use new flow control capacity before acknowledging it, causing strict HTTP/2 servers to
    fail the call.


## Version 4.1.1

_2019-09-05_

 *  Fix: Don't drop repeated headers when validating cached responses. In our Kotlin upgrade we
    introduced a regression where we iterated the number of unique header names rather than then
    number of unique headers. If you're using OkHttp's response cache this may impact you.

   */
  @get:JvmName("handshake") val handshake: Handshake?,
  /** Returns the HTTP headers. */
  @get:JvmName("headers") val headers: Headers,
  /**
   * Returns a non-null value if this response was passed to [Callback.onResponse] or returned
   * from [Call.execute]. Response bodies must be [closed][ResponseBody] and may
   * be consumed only once.
   *

 * received here. Use with @BeforeAll and @AfterAll, is not supported.
 *
 * There are 3 ids for instances
 * - The test instance default (passed into constructor)
 * - The test lifecycle default (passed into test method, plus @BeforeEach, @AfterEach)
 * - named instances with @MockWebServerInstance.
 */
@ExperimentalOkHttpApi
class MockWebServerExtension :

 * if (forceCacheResponse.code() != 504) {
 *   // The resource was cached! Show it.
 * } else {
 *   // The resource was not cached.
 * }
 * ```
 *
 * This technique works even better in situations where a stale response is better than no response.
 * To permit stale cached responses, use the `max-stale` directive with the maximum staleness in
 * seconds:
 *
 * ```java

 * This class currently pins a certificate's Subject Public Key Info as described on
 * [Adam Langley's Weblog][langley]. Pins are either base64 SHA-256 hashes as in
 * [HTTP Public Key Pinning (HPKP)][rfc_7469] or SHA-1 base64 hashes as in Chromium's
 * [static certificates][static_certificates].
 *
 * ## Setting up Certificate Pinning
 *

    }
  }

  // TODO GET preferred order - with tests to confirm this
  // 1. successful fresh cached GET response
  // 2. unsuccessful (404, 500) fresh cached GET response
  // 3. successful network response
  // 4. successful stale cached GET response
  // 5. unsuccessful response
  @Test
  fun usesCache() {
    val cache = Cache(cacheFs, "cache".toPath(), (100 * 1024).toLong())

        .onlyIfCached()
        .noTransform()
        .immutable()
        .build()
    assertThat(cacheControl.toString()).isEqualTo(
      "no-cache, no-store, max-age=1, max-stale=2, min-fresh=3, only-if-cached, " +
        "no-transform, immutable",
    )
    assertThat(cacheControl.noCache).isTrue()
    assertThat(cacheControl.noStore).isTrue()
    assertThat(cacheControl.maxAgeSeconds).isEqualTo(1)

        if (maxStaleSeconds != -1) append("max-stale=").append(maxStaleSeconds).append(", ")
        if (minFreshSeconds != -1) append("min-fresh=").append(minFreshSeconds).append(", ")
        if (onlyIfCached) append("only-if-cached, ")
        if (noTransform) append("no-transform, ")
        if (immutable) append("immutable, ")
        if (isEmpty()) return ""
        deleteRange(length - 2, length)
      }
    headerValue = result
  }

import okhttp3.Response
import okhttp3.internal.http.RealInterceptorChain

/**
 * Opens a connection to the target server and proceeds to the next interceptor. The network might
 * be used for the returned response, or to validate a cached response with a conditional GET.
 */
object ConnectInterceptor : Interceptor {
  @Throws(IOException::class)
  override fun intercept(chain: Interceptor.Chain): Response {
    val realChain = chain as RealInterceptorChain

      .assertRequestHeader("Accept-Charset", "UTF-8")
      .assertSentRequestAtMillis(request1SentAt, request1ReceivedAt)
      .assertReceivedResponseAtMillis(request1SentAt, request1ReceivedAt)

    // Check the cached response. Its request contains only the saved Vary headers.
    cacheHit.cacheResponse()
      .assertCode(200)
      .assertHeaders(
        Headers.Builder()
          .add("ETag", "v1")