does not allow to update mailchimp list id

app/models/mailchimp_setting.rb

@@ -1,6 +1,7 @@
 class MailchimpSetting < ActiveRecord::Base
   validates :mailchimp_api_key, :mailchimp_store_id, :mailchimp_list_id, :mailchimp_store_name, :cart_url, presence: true
   validate :validate_only_one_store, on: :create
+  validate :mailchimp_list_id_cannot_be_updated, on: :update
 
   def validate_only_one_store
     errors.add(:base, "only one store allowed") unless MailchimpSetting.count.zero?
@@ -13,4 +14,10 @@ def create_store_id
   def accout_name
     ::SpreeMailchimpEcommerce::GetAccountNameJob.perform_now(self)
   end
+
+  private
+
+  def mailchimp_list_id_cannot_be_updated
+    errors.add(:mailchimp_list_id, Spree.t(:can_not_be_updated)) if mailchimp_list_id_changed? && state == 'ready'
+  end
 end

config/locales/en.yml

@@ -0,0 +1,3 @@
+en:
+  spree:
+    can_not_be_updated: can't be updated

spec/factories/spree/mailchimp_setting_factory.rb

@@ -0,0 +1,12 @@
+FactoryBot.define do
+  factory :mailchimp_setting, class: MailchimpSetting do
+    sequence(:mailchimp_api_key) { |i| "#{FFaker::Internet.password}" + i.to_s }
+    sequence(:mailchimp_store_id) { |i| "#{FFaker::Internet.password}" + i.to_s }
+    sequence(:mailchimp_list_id) { |i| "#{FFaker::Internet.password}" + i.to_s }
+    sequence(:mailchimp_store_name) { |i| "store_no_#{i}" }
+    cart_url { FFaker::Internet.http_url }
+    mailchimp_account_name { FFaker::Internet.user_name }
+    state { 'inactive' }
+    mailchimp_store_email { FFaker::Internet.email }
+  end
+end

spec/models/mailchimp_setting_spec.rb

@@ -0,0 +1,39 @@
+require "spec_helper"
+
+describe MailchimpSetting, type: :model do
+  subject { create(:mailchimp_setting) }
+
+  describe "validations" do
+    it 'allows to save mailchimp setting' do
+      expect(subject.persisted?).to be true
+    end
+
+    it 'allows to destroy mailchimp setting' do
+      subject.destroy
+
+      expect(subject.destroyed?).to be true
+    end
+
+    context 'when mailchimp is synchronised' do
+      before { subject.update(state: 'ready') }
+
+      it 'does not allow to update mailchimp_list_id' do
+        subject.update(mailchimp_list_id: FFaker::Internet.password)
+
+        expect(subject.valid?).to be false
+        expect(subject.errors.to_h[:mailchimp_list_id]).to eq Spree.t(:can_not_be_updated)
+      end
+    end
+
+    context 'when mailchimp is not synchronised' do
+      let(:new_list_id) { FFaker::Internet.password }
+
+      it 'allows to update mailchimp_list_id' do
+        subject.update(mailchimp_list_id: new_list_id)
+
+        expect(subject.reload.mailchimp_list_id).to eq new_list_id
+      end
+    end
+  end
+end
+

spec/support/factory_bot.rb

@@ -1,7 +1,3 @@
-require "factory_bot"
-
-FactoryBot.find_definitions
-
 RSpec.configure do |config|
   config.include FactoryBot::Syntax::Methods
 end