Don't persist line item on promotion application

This is in service of the in-memory order updater.

Co-authored-by: Nick <nick@super.gd>
Co-authored-by: Sofia <sofia@super.gd>
Co-authored-by: Chris <chris@super.gd>
Co-authored-by: Jared <jared@super.gd>
Co-authored-by: Alistair <alistair@super.gd>
Co-authored-by: Adam <adam@super.gd>
Co-authored-by: An <andrew@super.gd>
Co-authored-by: Benjamin <benjamin@super.gd>

Author: 9 people

promotions/app/models/solidus_promotions/benefits/create_discounted_item.rb

@@ -28,9 +28,8 @@ def find_item(order)
         order.line_items.detect { |line_item| line_item.managed_by_order_benefit == self }
       end
 
-      # The enemy - create_item
       def create_item(order)
-        order.line_items.create!(quantity: determine_item_quantity(order), variant: variant, managed_by_order_benefit: self)
+        order.line_items.build(quantity: determine_item_quantity(order), variant: variant, managed_by_order_benefit: self)
       end
 
       def determine_item_quantity(order)

promotions/spec/models/solidus_promotions/benefits/create_discounted_item_spec.rb

@@ -6,21 +6,27 @@
   it { is_expected.to respond_to(:preferred_variant_id) }
 
   describe "#perform" do
-    let(:order) { create(:order_with_line_items) }
+    let!(:order) { create(:order_with_line_items) }
     let(:promotion) { create(:solidus_promotion) }
-    let(:benefit) { SolidusPromotions::Benefits::CreateDiscountedItem.new(preferred_variant_id: goodie.id, calculator: hundred_percent, promotion: promotion) }
+    let!(:benefit) { SolidusPromotions::Benefits::CreateDiscountedItem.new(preferred_variant_id: goodie.id, calculator: hundred_percent, promotion: promotion) }
     let(:hundred_percent) { SolidusPromotions::Calculators::Percent.new(preferred_percent: 100) }
     let(:goodie) { create(:variant) }
     subject { benefit.perform(order) }
 
     it "creates a line item with a hundred percent discount" do
-      expect { subject }.to change { order.line_items.count }.by(1)
+      expect { subject }.to change { order.line_items.size }.by(1)
       created_item = order.line_items.detect { |line_item| line_item.managed_by_order_benefit == benefit }
       expect(created_item.discountable_amount).to be_zero
     end
 
     it "never calls the order recalculator" do
       expect(order).not_to receive(:recalculate)
     end
+
+    it "does not persist changes to order" do
+      expect {
+        subject
+      }.not_to make_database_queries(manipulative: true)
+    end
   end
 end

promotions/spec/rails_helper.rb

@@ -5,6 +5,7 @@
 
 require "spec_helper"
 require "solidus_legacy_promotions"
+require 'db-query-matchers'
 
 # SOLIDUS DUMMY APP
 require "spree/testing_support/dummy_app"