added method to check if an item is selfarus

ruby/lib/gilded_rose.rb

@@ -56,6 +56,10 @@ class GildedRose
   def self.update_normal_quality(item)
     item.quality -= 1 unless item.quality.zero?
   end
+
+  def self.selfarus?(item)
+    !item.name.downcase.match( /selfarus/).nil?
+  end
 end
 
 class Item

ruby/spec/gilded_rose_spec.rb

@@ -94,12 +94,24 @@ let(:sulfarus) { Item.new('Sulfuras, Hand of Ragnaros', 50, 80) }
     end
 
     it 'does not update quality if quality == 0' do
-      item_double = double :item, name: "potato", sellIn: 1, quality: 0
+      item_double = double :item, name: "potato", sell_in: 1, quality: 0
       expect(item_double).not_to receive(:quality=).with(-1)
       GildedRose.update_normal_quality(item_double)
     end
 
   end
+
+  describe '#selfarus?' do
+    it 'returns true on a selfarus item' do
+      selfarus_double = double :selfarus, name: 'selfarus', sell_in: 50, quality: 80
+      expect(GildedRose.selfarus?(selfarus_double)).to eq true
+    end
+
+    it 'returns false on a non selfarus item' do
+      item_double = double :item, name: "potato", sell_in: 1, quality: 0
+      expect(GildedRose.selfarus?(item_double)).to eq false
+    end
+  end