Refactor billing plan stubbing for connection errors

ee/spec/features/billings/billing_plans_spec.rb

@@ -296,8 +296,7 @@ RSpec.describe 'Billing plan pages', :feature, :js do
       let!(:subscription) { create(:gitlab_subscription, namespace: namespace, hosted_plan: plan) }
 
       before do
-        stub_full_request("#{EE::SUBSCRIPTIONS_URL}/gitlab_plans?plan=#{plan.name}&namespace_id=#{namespace.id}")
-          .to_raise("Connection refused")
+        stub_billing_plans(namespace.id, plan.name, raise_error: 'Connection refused')
       end
 
       it 'renders an error page' do

ee/spec/features/groups/billing_spec.rb

@@ -114,9 +114,7 @@ RSpec.describe 'Groups > Billing', :js do
 
   context 'when CustomersDot is unavailable' do
     before do
-      stub_full_request("#{EE::SUBSCRIPTIONS_URL}/gitlab_plans?plan=#{plan}&namespace_id=#{group.id}")
-        .with(headers: { 'Accept' => 'application/json' })
-        .to_raise("Connection refused")
+      stub_billing_plans(group.id, plan, raise_error: 'Connection refused')
     end
 
     let(:plan) { 'bronze' }

ee/spec/support/helpers/subscription_portal_helpers.rb

@@ -27,10 +27,14 @@ module SubscriptionPortalHelpers
     end
   end
 
-  def stub_billing_plans(namespace_id, plan = 'free', plans_data = nil)
-    stub_full_request("#{EE::SUBSCRIPTIONS_URL}/gitlab_plans?namespace_id=#{namespace_id}&plan=#{plan}")
-      .with(headers: { 'Accept' => 'application/json' })
-      .to_return(status: 200, body: plans_data || plans_fixture)
+  def stub_billing_plans(namespace_id, plan = 'free', plans_data = nil, raise_error: nil)
+    stub = stub_full_request("#{EE::SUBSCRIPTIONS_URL}/gitlab_plans?namespace_id=#{namespace_id}&plan=#{plan}")
+             .with(headers: { 'Accept' => 'application/json' })
+    if raise_error
+      stub.to_raise(raise_error)
+    else
+      stub.to_return(status: 200, body: plans_data || plans_fixture)
+    end
   end
 
   private