require "minitest/autorun"

require 'buy_x_get_one_free_discount.rb'

class BuyXGetOneFreeDiscountTest < Minitest::Test
  def test_appropriate_discount_is_applied
    unit_price = 4.00
    (2..4).each do |trigger_quantity|
      discount = BuyXGetOneFreeDiscount.new(unit_price: unit_price, trigger_quantity: trigger_quantity)

      # Single discount at and above trigger quantity
      assert_equal unit_price, discount.discount_for_quantity(trigger_quantity)
      assert_equal unit_price, discount.discount_for_quantity(trigger_quantity + 1)
      assert_equal unit_price, discount.discount_for_quantity(trigger_quantity + trigger_quantity - 1)


      # No discount if less than trigger quantity
      assert_equal 0.00, discount.discount_for_quantity(trigger_quantity - 1)

      # Double discount if double trigger quantity
      assert_equal unit_price * 2, discount.discount_for_quantity(trigger_quantity * 2)
      assert_equal unit_price * 2, discount.discount_for_quantity((trigger_quantity * 2) + 1)
    end
  end
end