.trailers(headersOf("caboose", "xyz"))

    // Trailers always work for HTTP/2, but only for chunked bodies in HTTP/1.
    if (http2) {
      mockResponse.body("abc")
    } else {
      mockResponse.chunkedBody("abc", 1)
    }

    server.enqueue(mockResponse.build())

    val call =
      client.newCall(
        Request(
          url = server.url("/"),
          body = SlowRequestBody,
        ),