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

main.rb

@@ -5,5 +5,5 @@ checkout = Checkout.new()
 checkout.add(:PI5)
 checkout.add(:ZERO2W)
 
-checkout.items # ["PI5", "ZERO2W"]
+puts checkout.items # ["PI5", "ZERO2W"]
-checkout.total # 75.00
+puts checkout.total # 75.00

tests.rb

@@ -16,7 +16,22 @@ class TestCheckout < Minitest::Test
   def test_that_allowed_items_are_added
     @checkout.add(:PI5)
     @checkout.add(:ZERO2W)
+    @checkout.add(:PICO2)
 
-    assert_equal [:PI5, :ZERO2W].sort, @checkout.items.sort
+    assert_equal [:PI5, :ZERO2W, :PICO2].sort, @checkout.items.sort
+  end
+
+  def test_that_total_is_the_sum_of_all_items # Not accounting for discounts at the moment
+    @checkout.add(:PI5)     # 60.00
+    @checkout.add(:ZERO2W)  # 15.00
+    @checkout.add(:PICO2)   #  4.00
+                            # -----
+                            # 79.00 total
+
+    assert_equal 79.00, @checkout.total
+  end
+
+  def test_that_an_empty_checkout_total_is_zero
+    assert_equal 0.00, @checkout.total
   end
 end