Basic total generation, no discounts for now

checkout.rb

@@ -12,7 +12,7 @@ class Checkout
   end
 
   def add(item)
-    raise InvalidItem unless valid_item(item)
+    raise InvalidItem unless valid_item?(item)
     @items.push item
   end
 
@@ -20,9 +20,15 @@ class Checkout
     @items
   end
 
+  def total
+    @items.reduce(0.00) do |running_total, item|
+      running_total + AVAILABLE_ITEMS[item]
+    end
+  end
+
   private
 
-  def valid_item(item)
+  def valid_item?(item)
     return AVAILABLE_ITEMS.keys.include?(item)
   end
-end
+end