Add tests for order_items

app/models/order_item.rb

@@ -13,7 +13,7 @@ class OrderItem < ActiveRecord::Base
   belongs_to :product
 
   validates :product, presence: true
-  validates :count, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
+  validates :count, presence: true, numericality: { only_integer: true, greater_than_or_equal_to: 0 }
 
   after_create :remove_from_stock
 

spec/models/order_item_spec.rb

@@ -1,9 +1,46 @@
 describe OrderItem do
-  before :each do
-    @order_item = create :order_item
+  it 'has a valid factory' do
+    order_item = create :order_item
+    expect(order_item).to be_valid
   end
 
-  it 'has a valid factory' do
-    expect(@order_item).to be_valid
+  describe 'validations' do
+    before :each do
+      @order_item = create :order_item
+    end
+
+    it 'product should be present' do
+      @order_item.product = nil
+      expect(@order_item).to_not be_valid
+    end
+
+    describe 'count' do
+      it 'should be present' do
+        @order_item.count = nil
+        expect(@order_item).to_not be_valid
+      end
+
+      it 'should be positive' do
+        @order_item.count = -5
+        expect(@order_item).to_not be_valid
+      end
+    end
+  end
+
+  describe 'product stock' do
+    before :each do
+      @product = create :product
+      @count = rand 10
+      @order_item = build :order_item, product: @product, count: @count
+    end
+
+    it 'should decrement on create' do
+      expect{@order_item.save}.to change{@product.stock}.by(-@count)
+    end
+
+    it 'should increment on cancel' do
+      @order_item.save
+      expect{@order_item.cancel}.to change{@product.stock}.by(@count)
+    end
   end
 end