Receive and expect Stripe webhook events in your Rails system tests

something_system_spec.rb

require 'system_helper'

RSpec.describe 'Something', type: :system do
  it 'receives an event', :with_stripe_events do
    make_request_at_stripe
    wait_for_stripe_event { |e| e.type == 'charge.succeeded' }
    expect(...)
  end
end

with_stripe_events.rb

require 'stripe'
require 'stripe_event' # https://github.com/integrallis/stripe_event
require 'json'
require 'open3'

# Expects bin/stripe-{platform} to be relevant version of stripe-cli
# https://github.com/stripe/stripe-cli

class StripeCli
  class << self
    def debug?
      @debug ||= false
    end

    attr_writer :debug
  end

  def initialize(callback = nil, &block)
    @callback = callback || block
  end

  def self.boot!(&block)
    return if @instance

    @instance = new(&block).boot!
  end

  def self.kill!
    return unless @instance

    @instance.kill!
    @instance = nil
  end

  def boot!
    @cli_thread = Thread.new do
      puts "Booting Stripe CLI with #{cmd}" if debug?
      meth = debug? ? :popen2 : :popen2e

      Open3.send(meth, cmd) do |_in, out, _status|
        out.each do |line|
          case line
          when /^{/
            start_buffering(line)
          when /^}/
            json = flush_buffer(line)
            puts json if debug?

            begin
              event = Stripe::Event.construct_from(json, symbolize_names: true)
              @callback.call(event)
            rescue => e
              puts e.inspect
              puts e.backtrace if debug?
            end
          else
            write_to_buffer(line) if buffering?
          end
        end
      rescue => e
        puts e.inspect
        puts e.backtrace if debug?
      end
    end

    sleep 1 # wait for the cli to be mostly ready

    self
  end

  def kill!
    puts 'Killing Stripe CLI' if debug?
    @cli_thread.kill
  end

  private

  def debug?
    self.class.debug?
  end

  def cmd
    @cmd ||=
      begin
        cli = "bin/stripe-#{Gem::Platform.local.os}"
        "#{cli} listen -p --config spec/stripe.toml"
      end
  end

  def start_buffering(line)
    @object_buffer = '' + line
  end

  def write_to_buffer(line)
    @object_buffer += line
  end

  def flush_buffer(line)
    @object_buffer += line
    json = JSON.parse(@object_buffer)
    @object_buffer = nil

    json
  end

  def buffering?
    !!@object_buffer
  end
end

module WithStripeEventsHelpers
  def register_stripe_event(event)
    stripe_events.push(event)
  end

  def stripe_events
    @stripe_events ||= []
  end

  def wait_for_stripe_event
    Timeout.timeout(15) do
      loop do
        break if stripe_events.find { |event| yield(event) }

        sleep 0.1
      end
    rescue Timeout::Error
      puts 'Died waiting for Stripe event'
      raise
    end
  end
end

RSpec.configure do |config|
  config.include WithStripeEventsHelpers, with_stripe_events: true

  config.before(:each, with_stripe_events: true) do
    StripeCli.boot! do |event|
      register_stripe_event event
      StripeEvent.instrument(event)
    end
  end

  config.after(:each, with_stripe_events: true) do
    StripeCli.kill!
  end
end