override fun onResponse(
          call: Call,
          response: Response,
        ) {
          responses.offer(response.body.string())
        }
      }

    // Make the first request waiting until we get our auth challenge.
    val request = Request(server.url("/"))
    blockingAuthClient.newCall(request).enqueue(callback)
    val response1 = responses.take()
    assertThat(response1).isEqualTo("")

    val startNanos = System.nanoTime()
    sink.write(Buffer().writeUtf8("f"), 1)
    assertFailsWith<InterruptedIOException> {
      sink.flush() // This will time out waiting on the write window.
    }
    val elapsedNanos = System.nanoTime() - startNanos
    awaitWatchdogIdle()
    // 200ms delta
    assertThat(TimeUnit.NANOSECONDS.toMillis(elapsedNanos).toDouble())