Test customer balance query with guest orders

Guest orders also have an associated customer record that is created
by Spree::Order#ensure_customer at checkout. Subsequent orders will use
that one due to Spree::Order#associate_customer.

spec/factories/order_factory.rb

@@ -9,7 +9,7 @@ FactoryBot.define do
     user
     bill_address
     completed_at { nil }
-    email { user.email }
+    email { user&.email || customer.email }
 
     factory :order_with_totals do
       after(:create) do |order|

spec/services/customers_with_balance_spec.rb

@@ -12,14 +12,28 @@ describe CustomersWithBalance do
       let(:total) { 200.00 }
       let(:order_total) { 100.00 }
 
-      before do
-        create(:order, customer: customer, total: order_total, payment_total: 0)
-        create(:order, customer: customer, total: order_total, payment_total: 0)
+      context 'when non-guest order' do
+        before do
+          create(:order, customer: customer, total: order_total, payment_total: 0)
+          create(:order, customer: customer, total: order_total, payment_total: 0)
+        end
+
+        it 'returns the customer balance' do
+          customer = customers_with_balance.query.first
+          expect(customer.balance_value).to eq(-total)
+        end
       end
 
-      it 'returns the customer balance' do
-        customer = customers_with_balance.query.first
-        expect(customer.balance_value).to eq(-total)
+      context 'when guest order' do
+        before do
+          create(:order, customer: customer, user: nil, total: order_total, payment_total: 0)
+          create(:order, customer: customer, user: nil, total: order_total, payment_total: 0)
+        end
+
+        it 'returns the customer balance' do
+          customer = customers_with_balance.query.first
+          expect(customer.balance_value).to eq(-total)
+        end
       end
     end
 
@@ -28,14 +42,34 @@ describe CustomersWithBalance do
       let(:order_total) { 100.00 }
       let(:payment_total) { order_total }
 
-      before do
-        create(:order, customer: customer, total: order_total, payment_total: 0)
-        create(:order, customer: customer, total: order_total, payment_total: payment_total)
+      context 'when non-guest order' do
+        before do
+          create(:order, customer: customer, total: order_total, payment_total: 0)
+          create(:order, customer: customer, total: order_total, payment_total: payment_total)
+        end
+
+        it 'returns the customer balance' do
+          customer = customers_with_balance.query.first
+          expect(customer.balance_value).to eq(payment_total - total)
+        end
       end
 
-      it 'returns the customer balance' do
-        customer = customers_with_balance.query.first
-        expect(customer.balance_value).to eq(payment_total - total)
+      context 'when guest order' do
+        before do
+          create(:order, customer: customer, user: nil, total: order_total, payment_total: 0)
+          create(
+            :order,
+            customer: customer,
+            user: nil,
+            total: order_total,
+            payment_total: payment_total
+          )
+        end
+
+        it 'returns the customer balance' do
+          customer = customers_with_balance.query.first
+          expect(customer.balance_value).to eq(payment_total - total)
+        end
       end
     end
 
@@ -45,17 +79,44 @@ describe CustomersWithBalance do
       let(:payment_total) { 100.00 }
       let(:complete_orders_total) { order_total }
 
-      before do
-        create(:order, customer: customer, total: order_total, payment_total: 0)
-        create(
-          :order,
-          customer: customer,
-          total: order_total,
-          payment_total: order_total,
-          state: 'canceled'
-        )
+      context 'when non-guest order' do
+        before do
+          create(:order, customer: customer, total: order_total, payment_total: 0)
+          create(
+            :order,
+            customer: customer,
+            total: order_total,
+            payment_total: order_total,
+            state: 'canceled'
+          )
+        end
+
+        it 'returns the customer balance' do
+          customer = customers_with_balance.query.first
+          expect(customer.balance_value).to eq(payment_total - complete_orders_total)
+        end
       end
 
+      context 'when guest order' do
+        before do
+          create(:order, customer: customer, user: nil, total: order_total, payment_total: 0)
+          create(
+            :order,
+            customer: customer,
+            user: nil,
+            total: order_total,
+            payment_total: order_total,
+            state: 'canceled'
+          )
+        end
+
+        it 'returns the customer balance' do
+          customer = customers_with_balance.query.first
+          expect(customer.balance_value).to eq(payment_total - complete_orders_total)
+        end
+      end
+    end
+
       it 'returns the customer balance' do
         customer = customers_with_balance.query.first
         expect(customer.balance_value).to eq(payment_total - complete_orders_total)