Hello friends, Imagine you want to download a tar file from hex.pm website.

I have this function and do not want to install req hex plugin. as you see I find the "contents.tar.gz" and it is the binary of file.

  @spec download(download_type, pkg) :: okey_return | error_return
  def download(:hex, %{app: app, tag: tag_name}) when not is_nil(tag_name) do
    case build_url("https://repo.hex.pm/tarballs/#{app}-#{tag_name}.tar") do
      %Req.Response{status: 200, body: body} ->
        converted = Map.new(body, fn {key, value} -> {to_string(key), value} end)
        {:ok, converted["contents.tar.gz"]}

      _ ->
        mix_global_err()
    end
  end

And downloader function:

  defp build_url(location) do
    [base_url: location]
    |> Keyword.merge(Application.get_env(:mishka_installer, :downloader_req_options, []))
    |> Keyword.merge(Application.get_env(:mishka_installer, :proxy, []))
    |> Req.request!()
  end

Now I want to mock it, so this is the place I can not be able to fix.

One of my function test is what does not work:

body = [
        {~c"VERSION", "3"},
        {~c"CHECKSUM", "1D5EC32825E5AF1B5CF58933F4C918909BC79E4391EBE2B9315B02705145B18F"},
        {~c"metadata.config", "{<<\"app\">>,<<\"mishka_installer\">>}.\n{<<\"build_tools\">>"},
        {~c"contents.tar.gz", <<31, 139, 8, 0, 0, 0>>}
      ]

      body_iolist_to_binary =
        Enum.reduce(body, "", fn {key, value}, acc -> acc <> "#{key}:#{value}\n" end)
        |> :erlang.iolist_to_binary()

      Req.Test.expect(Downloader, fn conn ->
        conn
        |> Plug.Conn.put_resp_content_type("application/octet-stream")
        |> Plug.Conn.send_resp(200, body_iolist_to_binary)
      end)

If I put body directly I have error!! I have no idea how can simulate the hex output.

It should be noted my function works as well, my problem is located in testing this

Thank you in advance