Add tests for configurable mergeable orders finder

Adds specs to ensure a custom `mergeable_orders_finder_class` is used
when configured, verifies the default finder, and tests
`MergeableOrdersFinder#call` for correct order filtering behavior.

Signed-off-by: Thukten Singye <[email protected]>

Author: ThuktenSingye

core/spec/lib/spree/app_configuration_spec.rb

@@ -48,6 +48,10 @@
     expect(prefs.promotions).to be_a Spree::Core::NullPromotionConfiguration
   end
 
+  it 'uses mergeable orders finder class by default' do
+    expect(prefs.mergeable_orders_finder_class).to eq Spree::MergeableOrdersFinder
+  end
+
   context "deprecated preferences" do
     around do |example|
       Spree.deprecator.silence do

core/spec/models/spree/mergeable_orders_finder_spec.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+module Spree
+  RSpec.describe MergeableOrdersFinder do
+    let(:user) { create(:user) }
+    let(:store) { create(:store) }
+    let(:current_order) { create(:order, user: user, store: store) }
+    let(:subject) { Spree::MergeableOrdersFinder.new(user: user, store: store, current_order: current_order) }
+
+    describe '#call' do
+      let!(:incomplete_order1) { create(:order, user: user, store: store, state: 'cart') }
+      let!(:incomplete_order2) { create(:order, user: user, store: store, state: 'address') }
+      let!(:complete_order) { create(:order, user: user, store: store, state: 'complete').touch(:completed_at) }
+      let!(:other_store_order) { create(:order, user: user, state: 'cart') }
+
+      it 'returns incomplete orders from the same store' do
+        orders = subject.call
+        expect(orders).to include(incomplete_order1, incomplete_order2)
+        expect(orders).not_to include(current_order, complete_order, other_store_order)
+      end
+    end
+  end
+end

core/spec/models/spree/order_spec.rb

@@ -422,6 +422,44 @@ def merge!(other_order, user = nil)
         expect(order1.merge!(order2, user)).to eq([order1, order2, user])
       end
     end
+
+    describe 'mergeable_orders_finder_class customization' do
+      let(:user) { create(:user) }
+      let(:store) { create(:store) }
+      let(:current_order) { create(:order, user: user, store: store) }
+
+      before do
+        class TestMergeableOrdersFinder
+          def initialize(user:, store:, current_order:)
+            @user = user
+            @store = store
+            @current_order = current_order
+          end
+
+          def call
+            @user.orders.by_store(@store).where.not(id: @current_order.id).where('created_at > ?', 7.days.ago)
+          end
+        end
+        Spree::Config.mergeable_orders_finder_class = TestMergeableOrdersFinder
+      end
+
+      subject(:finder) do
+        Spree::Config.mergeable_orders_finder_class.new(
+          user: user,
+          store: store,
+          current_order: current_order
+        )
+      end
+
+      it 'uses the configured mergeable orders finder' do
+        old_order = create(:order, user: user, store: store, created_at: 8.days.ago)
+        recent_order = create(:order, user: user, store: store, created_at: 3.days.ago)
+
+        orders = finder.call
+        expect(orders).to include(recent_order)
+        expect(orders).not_to include(old_order, current_order)
+      end
+    end
   end
 
   describe "#ensure_updated_shipments" do