override fun contentType(): MediaType? = null

            override fun writeTo(sink: BufferedSink) {
              sink.writeUtf8("attempt " + attempt++)
            }

            override fun isOneShot(): Boolean = true
          },
      )
    val response = client.newCall(request).execute()
    assertThat(response.code).isEqualTo(503)
    assertThat(response.body.string()).isEqualTo("please retry")