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

I tested the stripe webhook signature outside of the controller context. One of the key parts is to pass real webhook secret in test environment to create the signature (just as stripe is creating it) that will be verified in tests. I am holding the real webhook secret under WEBHOOK_SECRET_STRIPE_LIVE_MODE. Without it, or with test mode webhook, I am getting the error Webhook signature verification failed

Note that I am using STRIPE_MODE to switch between test mode and live mode webhook secrets.

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