Update RSpec for Product Item model

spec/factories/product_item.rb

+FactoryGirl.define do
+  factory :product_item do
+    quantity 1
+    product
+    order
+  end
+end

spec/models/order_spec.rb

@@ -17,14 +17,13 @@ RSpec.describe Order, type: :model do
   end
 
   context 'custom methods' do
+    let(:user) { create(:user) }
+    let!(:order) { create(:order, user: user) }
+    let!(:product) { create(:product, quantity: 3, price: 10) }
+    let!(:product_item) { create(:product_item, product: product, order: order) }
+
     it 'has valid total_price' do
-      user = create(:user)
-      order = create(:order, user: user)
-      product = create(:product, quantity: 3, price: 10)
-      ProductItem.create(quantity: 2,
-                         product_id: product.id,
-                         order: order)
-      expect(order.total_price).to eq 20
+      expect(order.total_price).to eq 10
     end
   end
 end

spec/models/product_item_spec.rb

@@ -15,4 +15,18 @@ RSpec.describe ProductItem, type: :model do
     it { is_expected.to belong_to(:order) }
     it { is_expected.to belong_to(:product) }
   end
+
+  context 'custom methods' do
+    let!(:product) { create(:product, price: 10, quantity: 3) }
+    let!(:product_item) { create(:product_item, product: product) }
+
+    it 'has valid total_price' do
+      expect(product_item.total_price).to eq 10
+    end
+
+    it 'has valid update_product_quantity' do
+      product_item.update_product_quantity
+      expect(product.quantity).to eq 2
+    end
+  end
 end

spec/models/product_spec.rb

@@ -25,14 +25,22 @@ RSpec.describe Product, type: :model do
   context 'custom methods' do
     let!(:user) { create(:user) }
     let!(:other_user) { create(:user) }
-    let!(:product) { create(:product, quantity: 3, user: other_user) }
+    let!(:product) { create(:product, quantity: 3, user: user) }
 
     it 'has valid in_stock?' do
       expect(product.in_stock?(2)).to be_truthy
     end
 
+    it 'has invalid in_stock?' do
+      expect(product.in_stock?(4)).not_to be_truthy
+    end
+
     it 'has valid belongs_to_user?' do
-      expect(product.belongs_to_user?(user)).not_to be_truthy
+      expect(product.belongs_to_user?(user)).to be_truthy
+    end
+
+    it 'has invalid belongs_to_user?' do
+      expect(product.belongs_to_user?(other_user)).not_to be_truthy
     end
   end
 end