An example of how to mock external service errors

sample.rb

class MyService
  def send_request(number)
    # calls an external service and might encounter an error
    puts "... sending request ..."
  end

  def call_me_maybe(number)
    begin
      # first attempt
      self.send_request(number)
      return true
    rescue => exception
      begin
        # second attempt
        self.send_request(number)
        return true
      rescue => exception
        return false
      end
    end
  end
end

test '#call_me_maybe returns true when retry succeeds' do
  # arrange
  service = MyService.new()

  # somehow mock failure on first attempt
  # to validate the second attempt is tried out

  # act & assert
  assert service.call_me_maybe('123-456-7890')
end