modify_cassettes.rb

require "json"
require "yaml"

cassette_files = `git ls-files features/cassettes spec/vcr_cassettes | grep yml$`.split

p cassette_files

cassette_files.each do |filename|
  yaml = YAML.load_file filename
  yaml.fetch("http_interactions").each do |interaction|
    request = interaction.fetch("request")
    if request.fetch("method") == "post" && request.fetch("uri").match(/hermes.*messages$/)
      payload = JSON.parse request.fetch("body").fetch("string")
      unless payload["type"]
        request["body"]["string"].insert(-2, ',"type":"text"')
        File.open filename, 'w' do |file|
          file.write yaml.to_yaml
        end
      end
    end
  end
end