Add BulkDiscount

bulk_discount.rb

@@ -0,0 +1,10 @@
+class BulkDiscount
+  def initialize(unit_discount:, trigger_quantity: 2)
+    @unit_discount = unit_discount
+    @trigger_quantity = trigger_quantity.to_f
+  end
+
+  def discount_for_quantity(quantity)
+    quantity >= @trigger_quantity ? @unit_discount * quantity : 0.00
+  end
+end

buy_x_get_one_free_discount.rb

@@ -5,6 +5,6 @@ class BuyXGetOneFreeDiscount
   end
 
   def discount_for_quantity(quantity)
-    return (quantity / @trigger_quantity).floor * @unit_price
+    (quantity / @trigger_quantity).floor * @unit_price
   end
 end

test/bulk_discount_test.rb

@@ -0,0 +1,15 @@
+require "minitest/autorun"
+
+require 'bulk_discount.rb'
+
+class BulkDiscountTest < Minitest::Test
+  def test_appropriate_discount_is_applied
+    unit_discount = 0.75
+
+    discount = BulkDiscount.new(unit_discount: unit_discount, trigger_quantity: 4)
+
+    assert_equal 0.00, discount.discount_for_quantity(3)
+    assert_equal unit_discount * 4, discount.discount_for_quantity(4)
+    assert_equal unit_discount * 5, discount.discount_for_quantity(5)
+  end
+end

test/checkout_test.rb

@@ -2,6 +2,7 @@ require "minitest/autorun"
 
 require "checkout.rb"
 require "buy_x_get_one_free_discount.rb"
+require "bulk_discount.rb"
 
 class CheckoutTest < Minitest::Test
   def setup
@@ -22,7 +23,8 @@ class CheckoutTest < Minitest::Test
     @shop.add_product(
       Product.new(
         id: 'PICO2',
-        price: 4.00
+        price: 4.00,
+        discount: BulkDiscount.new(unit_discount: 0.50, trigger_quantity: 3)
       )
     )
     @checkout = Checkout.new(shop: @shop)
@@ -98,45 +100,26 @@ class CheckoutTest < Minitest::Test
   end
 
   def test_that_price_is_reduced_for_3_picos
-    skip
-
-    3.times do
-      @checkout.add(:PICO2) # 3.50 * 3 = 10.50
-    end
+    @checkout.add(product_id: 'PICO2', quantity: 3) # 3.50 * 3 = 10.50
 
     assert_equal 10.50, @checkout.total
   end
 
   def test_that_price_is_reduced_for_more_than_3_picos
-    skip
-
-    4.times do
-      @checkout.add(:PICO2) # 3.50 * 4 = 14
-    end
+    @checkout.add(product_id: 'PICO2', quantity: 4) # 3.50 * 4 = 14
 
     assert_equal 14.00, @checkout.total
   end
 
   def test_that_price_is_not_reduced_for_less_than_3_picos
-    skip
-
-    2.times do
-      @checkout.add(:PICO2) # 4.00 * 2 = 8
-    end
+    @checkout.add(product_id: 'PICO2', quantity: 2) # 4.00 * 2 = 8
 
     assert_equal 8.00, @checkout.total
   end
 
   def test_that_both_discounts_apply_at_the_same_time
-    skip
-
-    4.times do
-      @checkout.add(:ZERO2W) # 30.00 with BOGOF
-    end
-
-    3.times do
-      @checkout.add(:PICO2) # 10.50 with bulk discount
-    end
+    @checkout.add(product_id: 'ZERO2W', quantity: 4) # 30.00 with BOGOF
+    @checkout.add(product_id: 'PICO2', quantity: 3) # 10.50 with bulk discount
 
     assert_equal (30.00 + 10.50), @checkout.total
   end