class ActiveStorage::FixtureSet

def prepare(instance, **attributes)
  io = file_fixture(instance.filename.to_s).open
  instance.unfurl(io)
  instance.assign_attributes(attributes)
  instance.upload_without_unfurling(io)
  instance.attributes.transform_values { |value| value.is_a?(Hash) ? value.to_json : value }.compact.to_json
end