Test stripe webhook signature outside of controller context

stripe_webhook_signature_spec.rb

# Controlller
class Webhooks::StripeController < ApplicationController
  skip_before_action :verify_authenticity_token

  def index
    stripe_service = StripeService.new(
      request.env['HTTP_STRIPE_SIGNATURE'],
      request.body.read
    )

    render json: { message: stripe_service.message }, status: stripe_service.status
  end
end


# Service class
class StripeService
  attr_reader :message, :status

  def initialize(signature, request_body)
    @request_body = request_body
    @signature = signature
    @event = nil
    construct_event
  end

  private

  def construct_event
    endpoint_secret = ENV['STRIPE_MODE'] == 'live_mode' || Rails.env.test? ?
      ENV['WEBHOOK_SECRET_STRIPE_LIVE_MODE'] : ##### set live webhook secret for test environment
      ENV['WEBHOOK_SECRET_STRIPE_TEST_MODE']

    # verify_payload
    begin
      @event = Stripe::Event.construct_from(JSON.parse(@request_body, symbolize_names: true))
      @event = Stripe::Webhook.construct_event(@request_body, @signature, endpoint_secret)
    rescue JSON::ParserError => e
      @message = "⚠️  Webhook error while parsing basic request. #{e.message}"
      @status = 400
      return
    rescue Stripe::SignatureVerificationError => e
      @message = "⚠️  Webhook signature verification failed. #{e.message}"
      @status = 400
      return
    end

    case @event.type
    when 'some.stripe.event'
      # do your thing
    else
      puts "Unhandled event type: #{@event.type}"
    end

    @message = 'Success'
    @status = 200
  end
end


# Service spec
require 'rails_helper'
require 'openssl'
require 'base64'

describe StripeService do
  let!(:user) { create(:user, email: 'foo@foo.com') }

  context 'when a real webhook request is sent' do
    it 'returns a success message' do
      stripe_service = StripeService.new(
        signature,
        stripe_real_webhook_request
      )

      expect(stripe_service.message).to eq('Success')
      expect(stripe_service.status).to eq(200)
      # expect your objects have changed after handing event
    end
  end

  context 'when an invalid signature is sent' do
    it 'returns a failed message' do
      stripe_service = StripeService.new(
        'invalid_signature',
        stripe_real_webhook_request
      )

      expect(stripe_service.message).to include('Webhook signature verification failed')
      expect(stripe_service.status).to eq(400)
      # expect your objects did not change after handing event
    end
  end

  context 'when a payload is invalid' do
    it 'returns a failed message' do
      stripe_service = StripeService.new(
        signature,
        'invalid_payload'
      )

      expect(stripe_service.message).to include('Webhook error while parsing basic request')
      expect(stripe_service.status).to eq(400)
      # expect your objects did not change after handing event
    end
  end
end

def signature
  timestamp = Time.new
  stripe_signature = Stripe::Webhook::Signature.compute_signature(
    timestamp,
    stripe_real_webhook_request,
    ENV['WEBHOOK_SECRET_STRIPE_LIVE_MODE']
  )

  "t=#{timestamp.to_i},v1=#{stripe_signature}"
end

def stripe_real_webhook_request
  {
    "id": "evt_absdeabcdefabcdefabcdef",
    "object": "event",
    "api_version": "2023-10-16",
    "created": 1911556325,
    "data": {
      "object": {
        # get the object shape from stripe docs
      },
    "type": "some.stripe.event"
  }.to_json
end


# controller spec
require 'rails_helper'

RSpec.describe "Webhooks::StripeController", type: :request do
  describe "POST path/to/stripe/webhooks" do
    let(:stripe_service_mock) { instance_double(StripeService, message: 'Success', status: 200) }

    before do
      expect(StripeService).to receive(:new).and_return(stripe_service_mock)
    end

    it "returns http success" do
      post "/path/to/stripe/webhooks"
      expect(response).to have_http_status(:success)
    end
  end
end

Extracted from https://gist.github.com/ToTenMilan/576d92c56ceb676602157a3d29f5c1e0