diff --git a/core/app/models/spree/order_contents.rb b/core/app/models/spree/order_contents.rb
index 5151df63030..580e72387bc 100644
--- a/core/app/models/spree/order_contents.rb
+++ b/core/app/models/spree/order_contents.rb
@@ -1,39 +1,9 @@
 # frozen_string_literal: true
 
 module Spree
-  class OrderContents
-    attr_accessor :order
-
-    def initialize(order)
-      @order = order
-    end
-
-    # Add a line items to the order if there is inventory to do so
-    # and populate Promotions
-    #
-    # @param [Spree::Variant] variant The variant the line_item should
-    #   be associated with
-    # @param [Integer] quantity The line_item quantity
-    # @param [Hash] options Options for the adding proccess
-    #   Valid options:
-    #     shipment: [Spree::Shipment] LineItem target shipment
-    #
-    # @return [Spree::LineItem]
-    def add(variant, quantity = 1, options = {})
-      line_item = add_to_line_item(variant, quantity, options)
-      after_add_or_remove(line_item, options)
-    end
-
-    def remove(variant, quantity = 1, options = {})
-      line_item = remove_from_line_item(variant, quantity, options)
-      after_add_or_remove(line_item, options)
-    end
-
-    def remove_line_item(line_item, options = {})
-      order.line_items.destroy(line_item)
-      after_add_or_remove(line_item, options)
-    end
-
+  class OrderContents < Spree::SimpleOrderContents
+    # Updates the order's line items with the params passed in.
+    # Also runs the PromotionHandler::Cart.
     def update_cart(params)
       if order.update(params)
         unless order.completed?
@@ -43,7 +13,7 @@ def update_cart(params)
           # promotion rules would not be triggered.
           reload_totals
           order.check_shipments_and_restart_checkout
-          PromotionHandler::Cart.new(order).activate
+          ::Spree::PromotionHandler::Cart.new(order).activate
         end
         reload_totals
         true
@@ -52,76 +22,15 @@ def update_cart(params)
       end
     end
 
-    def advance
-      while @order.next; end
-    end
-
-    def approve(user: nil, name: nil)
-      if user.blank? && name.blank?
-        raise ArgumentError, 'user or name must be specified'
-      end
-
-      order.update!(
-        approver: user,
-        approver_name: name,
-        approved_at: Time.current
-      )
-    end
-
     private
 
     def after_add_or_remove(line_item, options = {})
       reload_totals
       shipment = options[:shipment]
       shipment.present? ? shipment.update_amounts : order.check_shipments_and_restart_checkout
-      PromotionHandler::Cart.new(order, line_item).activate
+      ::Spree::PromotionHandler::Cart.new(order, line_item).activate
       reload_totals
       line_item
     end
-
-    def reload_totals
-      @order.recalculate
-    end
-
-    def add_to_line_item(variant, quantity, options = {})
-      line_item = grab_line_item_by_variant(variant, false, options)
-
-      line_item ||= order.line_items.new(
-        quantity: 0,
-        variant: variant,
-        adjustments: [],
-      )
-
-      line_item.quantity += quantity.to_i
-      line_item.options = ActionController::Parameters.new(options).permit(PermittedAttributes.line_item_attributes).to_h
-
-      line_item.target_shipment = options[:shipment]
-      line_item.save!
-      line_item
-    end
-
-    def remove_from_line_item(variant, quantity, options = {})
-      line_item = grab_line_item_by_variant(variant, true, options)
-      line_item.quantity -= quantity
-      line_item.target_shipment = options[:shipment]
-
-      if line_item.quantity <= 0
-        order.line_items.destroy(line_item)
-      else
-        line_item.save!
-      end
-
-      line_item
-    end
-
-    def grab_line_item_by_variant(variant, raise_error = false, options = {})
-      line_item = order.find_line_item_by_variant(variant, options)
-
-      if !line_item.present? && raise_error
-        raise ActiveRecord::RecordNotFound, "Line item not found for variant #{variant.sku}"
-      end
-
-      line_item
-    end
   end
 end
diff --git a/core/app/models/spree/simple_order_contents.rb b/core/app/models/spree/simple_order_contents.rb
new file mode 100644
index 00000000000..6e50556342e
--- /dev/null
+++ b/core/app/models/spree/simple_order_contents.rb
@@ -0,0 +1,120 @@
+# frozen_string_literal: true
+
+module Spree
+  class SimpleOrderContents
+    attr_accessor :order
+
+    def initialize(order)
+      @order = order
+    end
+
+    # Add a line items to the order if there is inventory to do so
+    # and populate Promotions
+    #
+    # @param [Spree::Variant] variant The variant the line_item should
+    #   be associated with
+    # @param [Integer] quantity The line_item quantity
+    # @param [Hash] options Options for the adding proccess
+    #   Valid options:
+    #     shipment: [Spree::Shipment] LineItem target shipment
+    #
+    # @return [Spree::LineItem]
+    def add(variant, quantity = 1, options = {})
+      line_item = add_to_line_item(variant, quantity, options)
+      after_add_or_remove(line_item, options)
+    end
+
+    def remove(variant, quantity = 1, options = {})
+      line_item = remove_from_line_item(variant, quantity, options)
+      after_add_or_remove(line_item, options)
+    end
+
+    def remove_line_item(line_item, options = {})
+      order.line_items.destroy(line_item)
+      after_add_or_remove(line_item, options)
+    end
+
+    def update_cart(params)
+      if order.update(params)
+        unless order.completed?
+          order.line_items = order.line_items.select { |li| li.quantity > 0 }
+          order.check_shipments_and_restart_checkout
+        end
+        reload_totals
+        true
+      else
+        false
+      end
+    end
+
+    def advance
+      while @order.next; end
+    end
+
+    def approve(user: nil, name: nil)
+      if user.blank? && name.blank?
+        raise ArgumentError, 'user or name must be specified'
+      end
+
+      order.update!(
+        approver: user,
+        approver_name: name,
+        approved_at: Time.current
+      )
+    end
+
+    private
+
+    def after_add_or_remove(line_item, options = {})
+      shipment = options[:shipment]
+      shipment.present? ? shipment.update_amounts : order.check_shipments_and_restart_checkout
+      reload_totals
+      line_item
+    end
+
+    def reload_totals
+      @order.recalculate
+    end
+
+    def add_to_line_item(variant, quantity, options = {})
+      line_item = grab_line_item_by_variant(variant, false, options)
+
+      line_item ||= order.line_items.new(
+        quantity: 0,
+        variant: variant,
+        adjustments: [],
+      )
+
+      line_item.quantity += quantity.to_i
+      line_item.options = ActionController::Parameters.new(options).permit(PermittedAttributes.line_item_attributes).to_h
+
+      line_item.target_shipment = options[:shipment]
+      line_item.save!
+      line_item
+    end
+
+    def remove_from_line_item(variant, quantity, options = {})
+      line_item = grab_line_item_by_variant(variant, true, options)
+      line_item.quantity -= quantity
+      line_item.target_shipment = options[:shipment]
+
+      if line_item.quantity <= 0
+        order.line_items.destroy(line_item)
+      else
+        line_item.save!
+      end
+
+      line_item
+    end
+
+    def grab_line_item_by_variant(variant, raise_error = false, options = {})
+      line_item = order.find_line_item_by_variant(variant, options)
+
+      if !line_item.present? && raise_error
+        raise ActiveRecord::RecordNotFound, "Line item not found for variant #{variant.sku}"
+      end
+
+      line_item
+    end
+  end
+end
diff --git a/core/spec/models/spree/order_contents_spec.rb b/core/spec/models/spree/order_contents_spec.rb
index eb34512f870..472a00d49a3 100644
--- a/core/spec/models/spree/order_contents_spec.rb
+++ b/core/spec/models/spree/order_contents_spec.rb
@@ -12,76 +12,6 @@
   subject(:order_contents) { described_class.new(order) }
 
   context "#add" do
-    context 'given quantity is not explicitly provided' do
-      it 'should add one line item' do
-        line_item = subject.add(variant)
-        expect(line_item.quantity).to eq(1)
-        expect(order.line_items.size).to eq(1)
-      end
-    end
-
-    context 'given a shipment' do
-      let!(:shipment) { create(:shipment, order: order) }
-
-      it "ensure shipment calls update_amounts instead of order calling check_shipments_and_restart_checkout" do
-        expect(subject.order).to_not receive(:check_shipments_and_restart_checkout)
-        expect(shipment).to receive(:update_amounts).at_least(:once)
-        subject.add(variant, 1, shipment: shipment)
-      end
-
-      context "with quantity=1" do
-        it "creates correct inventory" do
-          subject.add(variant, 1, shipment: shipment)
-          expect(order.inventory_units.count).to eq(1)
-        end
-      end
-
-      context "with quantity=2" do
-        it "creates correct inventory" do
-          subject.add(variant, 2, shipment: shipment)
-          expect(order.inventory_units.count).to eq(2)
-        end
-      end
-
-      context "called multiple times" do
-        it "creates correct inventory" do
-          subject.add(variant, 1, shipment: shipment)
-          subject.add(variant, 1, shipment: shipment)
-          expect(order.inventory_units.count).to eq(2)
-        end
-      end
-    end
-
-    context 'not given a shipment' do
-      it "ensures updated shipments" do
-        expect(subject.order).to receive(:check_shipments_and_restart_checkout)
-        subject.add(variant)
-      end
-    end
-
-    it 'should add line item if one does not exist' do
-      line_item = subject.add(variant, 1)
-      expect(line_item.quantity).to eq(1)
-      expect(order.line_items.size).to eq(1)
-    end
-
-    it 'should update line item if one exists' do
-      subject.add(variant, 1)
-      line_item = subject.add(variant, 1)
-      expect(line_item.quantity).to eq(2)
-      expect(order.line_items.size).to eq(1)
-    end
-
-    it "should update order totals" do
-      expect(order.item_total.to_f).to eq(0.00)
-      expect(order.total.to_f).to eq(0.00)
-
-      subject.add(variant, 1)
-
-      expect(order.item_total.to_f).to eq(19.99)
-      expect(order.total.to_f).to eq(19.99)
-    end
-
     context "running promotions" do
       let(:promotion) { create(:promotion, apply_automatically: true) }
       let(:calculator) { Spree::Calculator::FlatRate.new(preferred_amount: 10) }
@@ -113,151 +43,6 @@
         include_context "discount changes order total"
       end
     end
-
-    describe 'tax calculations' do
-      let!(:zone) { create(:global_zone) }
-      let!(:tax_rate) do
-        create(:tax_rate, zone: zone, tax_categories: [variant.tax_category])
-      end
-
-      context 'when the order has a taxable address' do
-        before do
-          expect(order.tax_address.country_id).to be_present
-        end
-
-        it 'creates a tax adjustment' do
-          order_contents.add(variant)
-          line_item = order.find_line_item_by_variant(variant)
-          expect(line_item.adjustments.tax.count).to eq(1)
-        end
-      end
-
-      context 'when the order does not have a taxable address' do
-        before do
-          order.update!(ship_address: nil, bill_address: nil)
-          expect(order.tax_address.country_id).to be_nil
-        end
-
-        it 'creates a tax adjustment' do
-          order_contents.add(variant)
-          line_item = order.find_line_item_by_variant(variant)
-          expect(line_item.adjustments.tax.count).to eq(0)
-        end
-      end
-    end
-  end
-
-  context "#remove" do
-    context "given an invalid variant" do
-      it "raises an exception" do
-        expect {
-          subject.remove(variant, 1)
-        }.to raise_error(ActiveRecord::RecordNotFound)
-      end
-    end
-
-    context 'given quantity is not explicitly provided' do
-      it 'should remove one line item' do
-        line_item = subject.add(variant, 3)
-        subject.remove(variant)
-
-        expect(line_item.reload.quantity).to eq(2)
-      end
-    end
-
-    context 'given a shipment' do
-      it "ensure shipment calls update_amounts instead of order calling check_shipments_and_restart_checkout" do
-        subject.add(variant, 1)
-        shipment = create(:shipment)
-        expect(subject.order).to_not receive(:check_shipments_and_restart_checkout)
-        expect(shipment).to receive(:update_amounts)
-        subject.remove(variant, 1, shipment: shipment)
-      end
-    end
-
-    context 'not given a shipment' do
-      it "ensures updated shipments" do
-        subject.add(variant, 1)
-        expect(subject.order).to receive(:check_shipments_and_restart_checkout)
-        subject.remove(variant)
-      end
-    end
-
-    it 'should reduce line_item quantity if quantity is less the line_item quantity' do
-      line_item = subject.add(variant, 3)
-      subject.remove(variant, 1)
-
-      expect(line_item.reload.quantity).to eq(2)
-    end
-
-    it 'should remove line_item if quantity matches line_item quantity' do
-      subject.add(variant, 1)
-      subject.remove(variant, 1)
-
-      expect(order.reload.find_line_item_by_variant(variant)).to be_nil
-    end
-
-    it 'should remove line_item if quantity is greater than line_item quantity' do
-      subject.add(variant, 1)
-      subject.remove(variant, 2)
-
-      expect(order.reload.find_line_item_by_variant(variant)).to be_nil
-    end
-
-    it "should update order totals" do
-      expect(order.item_total.to_f).to eq(0.00)
-      expect(order.total.to_f).to eq(0.00)
-
-      subject.add(variant, 2)
-
-      expect(order.item_total.to_f).to eq(39.98)
-      expect(order.total.to_f).to eq(39.98)
-
-      subject.remove(variant, 1)
-      expect(order.item_total.to_f).to eq(19.99)
-      expect(order.total.to_f).to eq(19.99)
-    end
-  end
-
-  context "#remove_line_item" do
-    context 'given a shipment' do
-      it "ensure shipment calls update_amounts instead of order calling check_shipments_and_restart_checkout" do
-        line_item = subject.add(variant, 1)
-        shipment = create(:shipment)
-        expect(subject.order).to_not receive(:check_shipments_and_restart_checkout)
-        expect(shipment).to receive(:update_amounts)
-        subject.remove_line_item(line_item, shipment: shipment)
-      end
-    end
-
-    context 'not given a shipment' do
-      it "ensures updated shipments" do
-        line_item = subject.add(variant, 1)
-        expect(subject.order).to receive(:check_shipments_and_restart_checkout)
-        subject.remove_line_item(line_item)
-      end
-    end
-
-    it 'should remove line_item' do
-      line_item = subject.add(variant, 1)
-      subject.remove_line_item(line_item)
-
-      expect(order.reload.line_items).to_not include(line_item)
-    end
-
-    it "should update order totals" do
-      expect(order.item_total.to_f).to eq(0.00)
-      expect(order.total.to_f).to eq(0.00)
-
-      line_item = subject.add(variant, 2)
-
-      expect(order.item_total.to_f).to eq(39.98)
-      expect(order.total.to_f).to eq(39.98)
-
-      subject.remove_line_item(line_item)
-      expect(order.item_total.to_f).to eq(0.00)
-      expect(order.total.to_f).to eq(0.00)
-    end
   end
 
   context "update cart" do
@@ -321,48 +106,4 @@
       }.to change { order.payment_state }
     end
   end
-
-  describe "#approve" do
-    context 'when a name is supplied' do
-      it 'approves the order' do
-        order.contents.approve(name: 'Jordan')
-        expect(order.approver).to be_nil
-        expect(order.approver_name).to eq('Jordan')
-        expect(order.approved_at).to be_present
-        expect(order.approved?).to be_truthy
-      end
-    end
-
-    context 'when a user is supplied' do
-      let(:user) { create(:user) }
-
-      it 'approves the order' do
-        order.contents.approve(user: user)
-        expect(order.approver).to eq(user)
-        expect(order.approver_name).to be_nil
-        expect(order.approved_at).to be_present
-        expect(order.approved?).to be_truthy
-      end
-    end
-
-    context 'when a user and a name are supplied' do
-      let(:user) { create(:user) }
-
-      it 'approves the order' do
-        order.contents.approve(user: user, name: 'Jordan')
-        expect(order.approver).to eq(user)
-        expect(order.approver_name).to eq('Jordan')
-        expect(order.approved_at).to be_present
-        expect(order.approved?).to be_truthy
-      end
-    end
-
-    context 'when neither a user nor a name are supplied' do
-      it 'raises' do
-        expect {
-          order.contents.approve
-        }.to raise_error(ArgumentError, 'user or name must be specified')
-      end
-    end
-  end
 end
diff --git a/core/spec/models/spree/simple_order_contents_spec.rb b/core/spec/models/spree/simple_order_contents_spec.rb
new file mode 100644
index 00000000000..812b5fa2b8a
--- /dev/null
+++ b/core/spec/models/spree/simple_order_contents_spec.rb
@@ -0,0 +1,336 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe Spree::SimpleOrderContents, type: :model do
+  let!(:store) { create :store }
+  let(:order) { create(:order) }
+  let(:variant) { create(:variant) }
+  let!(:stock_location) { variant.stock_locations.first }
+  let(:stock_location_2) { create(:stock_location) }
+
+  subject(:order_contents) { described_class.new(order) }
+
+  context "#add" do
+    context 'given quantity is not explicitly provided' do
+      it 'should add one line item' do
+        line_item = subject.add(variant)
+        expect(line_item.quantity).to eq(1)
+        expect(order.line_items.size).to eq(1)
+      end
+    end
+
+    context 'given a shipment' do
+      let!(:shipment) { create(:shipment, order: order) }
+
+      it "ensure shipment calls update_amounts instead of order calling check_shipments_and_restart_checkout" do
+        expect(subject.order).to_not receive(:check_shipments_and_restart_checkout)
+        expect(shipment).to receive(:update_amounts).at_least(:once)
+        subject.add(variant, 1, shipment: shipment)
+      end
+
+      context "with quantity=1" do
+        it "creates correct inventory" do
+          subject.add(variant, 1, shipment: shipment)
+          expect(order.inventory_units.count).to eq(1)
+        end
+      end
+
+      context "with quantity=2" do
+        it "creates correct inventory" do
+          subject.add(variant, 2, shipment: shipment)
+          expect(order.inventory_units.count).to eq(2)
+        end
+      end
+
+      context "called multiple times" do
+        it "creates correct inventory" do
+          subject.add(variant, 1, shipment: shipment)
+          subject.add(variant, 1, shipment: shipment)
+          expect(order.inventory_units.count).to eq(2)
+        end
+      end
+    end
+
+    context 'not given a shipment' do
+      it "ensures updated shipments" do
+        expect(subject.order).to receive(:check_shipments_and_restart_checkout)
+        subject.add(variant)
+      end
+    end
+
+    it 'should add line item if one does not exist' do
+      line_item = subject.add(variant, 1)
+      expect(line_item.quantity).to eq(1)
+      expect(order.line_items.size).to eq(1)
+    end
+
+    it 'should update line item if one exists' do
+      subject.add(variant, 1)
+      line_item = subject.add(variant, 1)
+      expect(line_item.quantity).to eq(2)
+      expect(order.line_items.size).to eq(1)
+    end
+
+    it "should update order totals" do
+      expect(order.item_total.to_f).to eq(0.00)
+      expect(order.total.to_f).to eq(0.00)
+
+      subject.add(variant, 1)
+
+      expect(order.item_total.to_f).to eq(19.99)
+      expect(order.total.to_f).to eq(19.99)
+    end
+
+    describe 'tax calculations' do
+      let!(:zone) { create(:global_zone) }
+      let!(:tax_rate) do
+        create(:tax_rate, zone: zone, tax_categories: [variant.tax_category])
+      end
+
+      context 'when the order has a taxable address' do
+        before do
+          expect(order.tax_address.country_id).to be_present
+        end
+
+        it 'creates a tax adjustment' do
+          order_contents.add(variant)
+          line_item = order.find_line_item_by_variant(variant)
+          expect(line_item.adjustments.tax.count).to eq(1)
+        end
+      end
+
+      context 'when the order does not have a taxable address' do
+        before do
+          order.update!(ship_address: nil, bill_address: nil)
+          expect(order.tax_address.country_id).to be_nil
+        end
+
+        it 'creates a tax adjustment' do
+          order_contents.add(variant)
+          line_item = order.find_line_item_by_variant(variant)
+          expect(line_item.adjustments.tax.count).to eq(0)
+        end
+      end
+    end
+  end
+
+  context "#remove" do
+    context "given an invalid variant" do
+      it "raises an exception" do
+        expect {
+          subject.remove(variant, 1)
+        }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+    end
+
+    context 'given quantity is not explicitly provided' do
+      it 'should remove one line item' do
+        line_item = subject.add(variant, 3)
+        subject.remove(variant)
+
+        expect(line_item.reload.quantity).to eq(2)
+      end
+    end
+
+    context 'given a shipment' do
+      it "ensure shipment calls update_amounts instead of order calling check_shipments_and_restart_checkout" do
+        subject.add(variant, 1)
+        shipment = create(:shipment)
+        expect(subject.order).to_not receive(:check_shipments_and_restart_checkout)
+        expect(shipment).to receive(:update_amounts)
+        subject.remove(variant, 1, shipment: shipment)
+      end
+    end
+
+    context 'not given a shipment' do
+      it "ensures updated shipments" do
+        subject.add(variant, 1)
+        expect(subject.order).to receive(:check_shipments_and_restart_checkout)
+        subject.remove(variant)
+      end
+    end
+
+    it 'should reduce line_item quantity if quantity is less the line_item quantity' do
+      line_item = subject.add(variant, 3)
+      subject.remove(variant, 1)
+
+      expect(line_item.reload.quantity).to eq(2)
+    end
+
+    it 'should remove line_item if quantity matches line_item quantity' do
+      subject.add(variant, 1)
+      subject.remove(variant, 1)
+
+      expect(order.reload.find_line_item_by_variant(variant)).to be_nil
+    end
+
+    it 'should remove line_item if quantity is greater than line_item quantity' do
+      subject.add(variant, 1)
+      subject.remove(variant, 2)
+
+      expect(order.reload.find_line_item_by_variant(variant)).to be_nil
+    end
+
+    it "should update order totals" do
+      expect(order.item_total.to_f).to eq(0.00)
+      expect(order.total.to_f).to eq(0.00)
+
+      subject.add(variant, 2)
+
+      expect(order.item_total.to_f).to eq(39.98)
+      expect(order.total.to_f).to eq(39.98)
+
+      subject.remove(variant, 1)
+      expect(order.item_total.to_f).to eq(19.99)
+      expect(order.total.to_f).to eq(19.99)
+    end
+  end
+
+  context "#remove_line_item" do
+    context 'given a shipment' do
+      it "ensure shipment calls update_amounts instead of order calling check_shipments_and_restart_checkout" do
+        line_item = subject.add(variant, 1)
+        shipment = create(:shipment)
+        expect(subject.order).to_not receive(:check_shipments_and_restart_checkout)
+        expect(shipment).to receive(:update_amounts)
+        subject.remove_line_item(line_item, shipment: shipment)
+      end
+    end
+
+    context 'not given a shipment' do
+      it "ensures updated shipments" do
+        line_item = subject.add(variant, 1)
+        expect(subject.order).to receive(:check_shipments_and_restart_checkout)
+        subject.remove_line_item(line_item)
+      end
+    end
+
+    it 'should remove line_item' do
+      line_item = subject.add(variant, 1)
+      subject.remove_line_item(line_item)
+
+      expect(order.reload.line_items).to_not include(line_item)
+    end
+
+    it "should update order totals" do
+      expect(order.item_total.to_f).to eq(0.00)
+      expect(order.total.to_f).to eq(0.00)
+
+      line_item = subject.add(variant, 2)
+
+      expect(order.item_total.to_f).to eq(39.98)
+      expect(order.total.to_f).to eq(39.98)
+
+      subject.remove_line_item(line_item)
+      expect(order.item_total.to_f).to eq(0.00)
+      expect(order.total.to_f).to eq(0.00)
+    end
+  end
+
+  context "update cart" do
+    let!(:shirt) { subject.add variant, 1 }
+
+    let(:params) do
+      { line_items_attributes: {
+        "0" => { id: shirt.id, quantity: 3 }
+      } }
+    end
+
+    it "changes item quantity" do
+      subject.update_cart params
+      expect(shirt.reload.quantity).to eq 3
+    end
+
+    it "updates order totals" do
+      expect {
+        subject.update_cart params
+      }.to change { subject.order.total }
+    end
+
+    context "submits item quantity 0" do
+      let(:params) do
+        { line_items_attributes: {
+          "0" => { id: shirt.id, quantity: 0 }
+        } }
+      end
+
+      it "removes item from order" do
+        expect {
+          subject.update_cart params
+        }.to change { subject.order.line_items.count }
+      end
+    end
+
+    it "ensures updated shipments" do
+      expect(subject.order).to receive(:check_shipments_and_restart_checkout)
+      subject.update_cart params
+    end
+  end
+
+  context "completed order" do
+    let(:order) do
+      Spree::Order.create!(
+        state: 'complete',
+        completed_at: Time.current,
+        email: "test@example.com"
+      )
+    end
+
+    before { order.shipments.create! stock_location_id: variant.stock_location_ids.first }
+
+    it "updates order payment state" do
+      expect {
+        subject.add variant
+      }.to change { order.payment_state }
+
+      expect {
+        subject.remove variant
+      }.to change { order.payment_state }
+    end
+  end
+
+  describe "#approve" do
+    context 'when a name is supplied' do
+      it 'approves the order' do
+        order.contents.approve(name: 'Jordan')
+        expect(order.approver).to be_nil
+        expect(order.approver_name).to eq('Jordan')
+        expect(order.approved_at).to be_present
+        expect(order.approved?).to be_truthy
+      end
+    end
+
+    context 'when a user is supplied' do
+      let(:user) { create(:user) }
+
+      it 'approves the order' do
+        order.contents.approve(user: user)
+        expect(order.approver).to eq(user)
+        expect(order.approver_name).to be_nil
+        expect(order.approved_at).to be_present
+        expect(order.approved?).to be_truthy
+      end
+    end
+
+    context 'when a user and a name are supplied' do
+      let(:user) { create(:user) }
+
+      it 'approves the order' do
+        order.contents.approve(user: user, name: 'Jordan')
+        expect(order.approver).to eq(user)
+        expect(order.approver_name).to eq('Jordan')
+        expect(order.approved_at).to be_present
+        expect(order.approved?).to be_truthy
+      end
+    end
+
+    context 'when neither a user nor a name are supplied' do
+      it 'raises' do
+        expect {
+          order.contents.approve
+        }.to raise_error(ArgumentError, 'user or name must be specified')
+      end
+    end
+  end
+end
diff --git a/legacy_promotions/lib/solidus_legacy_promotions/engine.rb b/legacy_promotions/lib/solidus_legacy_promotions/engine.rb
index 2f897653ee9..b643b94d718 100644
--- a/legacy_promotions/lib/solidus_legacy_promotions/engine.rb
+++ b/legacy_promotions/lib/solidus_legacy_promotions/engine.rb
@@ -45,5 +45,9 @@ class Engine < ::Rails::Engine
     initializer "solidus_legacy_promotions.assets" do |app|
       app.config.assets.precompile << "solidus_legacy_promotions/manifest.js"
     end
+
+    initializer "solidus_legacy_promotions", after: "spree.load_config_initializers" do
+      Spree::Config.order_contents_class = "Spree::OrderContents"
+    end
   end
 end