@Test fun isProbablyUtf8() {
    assertThat(Buffer().isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeUtf8("abc").isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeUtf8("new\r\nlines").isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeUtf8("white\t space").isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeUtf8("Слава Україні!").isProbablyUtf8(16L)).isTrue()
    assertThat(Buffer().writeByte(0x80).isProbablyUtf8(16L)).isTrue()

      requestBody.writeUtf8("request A\n")
      requestBody.flush()
      val responseBody = response.body.source()
      assertThat(responseBody.readUtf8Line())
        .isEqualTo("response B")
      requestBody.writeUtf8("request C\n")
      requestBody.flush()
      assertThat(responseBody.readUtf8Line())
        .isEqualTo("response D")
      requestBody.writeUtf8("request E\n")
      requestBody.flush()

        sink.writeUtf8(url.toString()).writeByte('\n'.code)
        sink.writeUtf8(requestMethod).writeByte('\n'.code)
        sink.writeDecimalLong(varyHeaders.size.toLong()).writeByte('\n'.code)
        for (i in 0 until varyHeaders.size) {
          sink
            .writeUtf8(varyHeaders.name(i))
            .writeUtf8(": ")
            .writeUtf8(varyHeaders.value(i))
            .writeByte('\n'.code)

        socket.sink.buffer().use { sink ->
          socket.source.buffer().use { source ->
            sink.writeUtf8("client says hello\n")
            sink.flush()

            assertThat(source.readUtf8Line()).isEqualTo("server says hello")

            sink.writeUtf8("client says goodbye\n")
            sink.flush()

            assertThat(source.readUtf8Line()).isEqualTo("server says goodbye")

    server.enqueue(MockResponse())
    val body: RequestBody =
      object : RequestBody() {
        override fun contentType() = PLAIN

        override fun writeTo(sink: BufferedSink) {
          sink.writeUtf8("Hi!")
        }
      }
    val response = client.newCall(request().post(body).build()).execute()
    response.body.close()
    applicationLogs
      .assertLogEqual("--> POST $url")

    vararg bodyLines: String,
  ) {
    filesystem.write(journalFile) {
      writeUtf8(
        """
        |$magic
        |$version
        |$appVersion
        |$valueCount
        |$blank
        |
        """.trimMargin(),
      )
      for (line in bodyLines) {
        writeUtf8(line)
        writeUtf8("\n")
      }
    }
  }

          override fun contentType() = MEDIA_TYPE_MARKDOWN

          override fun writeTo(sink: BufferedSink) {
            sink.writeUtf8("Numbers\n")
            sink.writeUtf8("-------\n")
            for (i in 2..997) {
              sink.writeUtf8(String.format(" * $i = ${factor(i)}\n"))
            }
          }

          private fun factor(n: Int): String {
            for (i in 2 until n) {

      }
    }

  private inline fun <T> assertOnPath(
    content: String? = null,
    fn: (okio.Path) -> T,
  ): T {
    FileSystem.SYSTEM.write(filePath) {
      if (content != null) {
        writeUtf8(content)
      }
    }

    return fn(filePath)
  }

      override fun write(
        source: Buffer,
        byteCount: Long,
      ) {
        original.writeUtf8(source.readUtf8(byteCount).uppercase())
      }
    }

  private fun gzip(data: String): Buffer {
    val result = Buffer()
    val sink = GzipSink(result).buffer()
    sink.writeUtf8(data)
    sink.close()
    return result
  }

  private fun addInterceptor(
    network: Boolean,

  private object SlowRequestBody : RequestBody() {
    override fun contentType(): MediaType? = null

    override fun writeTo(sink: BufferedSink) {
      for (i in 0 until 50) {
        sink.writeUtf8("abc")
        sink.flush()
        Thread.sleep(100)
      }
      fail("")
    }
  }