ruby-checkout/test/checkout_test.rb

require "minitest/autorun"

require "checkout.rb"
require "buy_x_get_one_free_discount.rb"
require "bulk_discount.rb"

class CheckoutTest < Minitest::Test
  def setup
    @shop = Shop.new
    @shop.add_product(
      Product.new(
        id: 'PI5',
        price: 60.00
      )
    )
    @shop.add_product(
      Product.new(
        id: 'ZERO2W',
        price: 15.00,
        discount: BuyXGetOneFreeDiscount.new(unit_price: 15.00, trigger_quantity: 2)
      )
    )
    @shop.add_product(
      Product.new(
        id: 'PICO2',
        price: 4.00,
        discount: BulkDiscount.new(unit_discount: 0.50, trigger_quantity: 3)
      )
    )
    @checkout = Checkout.new(shop: @shop)
  end

  def test_that_unknown_items_cannot_be_added
    assert_raises Checkout::InvalidItem do
      @checkout.add(product_id: 'PI5000')
    end
  end

  def test_that_nil_is_not_allowed_to_be_added
    assert_raises Checkout::InvalidItem do
      @checkout.add(product_id: nil)
    end
  end

  def test_that_allowed_items_are_added
    @checkout.add(product_id: 'PI5')
    @checkout.add(product_id: 'ZERO2W')
    @checkout.add(product_id: 'PICO2')

    assert_equal({ 'PI5' => 1, 'ZERO2W' => 1, 'PICO2' => 1 }.sort, @checkout.item_quantities.sort)
  end

  def test_that_multiples_can_be_added_at_once
    @checkout.add(product_id: 'PI5', quantity: 5)
    assert_equal({ 'PI5' => 5 }.sort, @checkout.item_quantities.sort)

    @checkout.add(product_id: 'PI5', quantity: 5)
    assert_equal({ 'PI5' => 10 }.sort, @checkout.item_quantities.sort)
  end

  def test_that_total_is_the_sum_of_all_items_when_no_discounts_apply
    @checkout.add(product_id: 'PI5')    # 60.00
    @checkout.add(product_id: 'ZERO2W') # 15.00
    @checkout.add(product_id: '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

  def test_that_we_can_empty_the_checkout
    @checkout.add(product_id: 'PI5')
    @checkout.add(product_id: 'ZERO2W')
    @checkout.add(product_id: 'PICO2')

    refute_empty @checkout.items

    @checkout.clear

    assert_empty @checkout.items

  end

  # Discounts

  def test_that_bogof_applied
    @checkout.add(product_id: 'ZERO2W', quantity: 4) # Should remove 2 Zeros

    assert_equal 30.00, @checkout.total
  end

  def test_that_bogof_applied_with_odd_number
    @checkout.add(product_id: 'ZERO2W', quantity: 5) # Should still remove 2 Zeros, 5th is full price

    assert_equal 45.00, @checkout.total
  end

  def test_that_price_is_reduced_for_3_picos
    @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
    @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
    @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
    @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

  # Item removal

  def test_that_removing_an_item_not_in_the_checkout_removes_nothing
    skip

    @checkout.add(:PICO2)
    @checkout.remove(:PI5)

    assert_equal [:PICO2], @checkout.items
  end

  def test_that_items_are_removed_one_by_one
    skip

    4.times do
      @checkout.add(:ZERO2W)
    end

    3.times do
      @checkout.add(:PICO2)
    end

    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W, :ZERO2W, :PICO2, :PICO2, :PICO2].sort, @checkout.items.sort

    @checkout.remove(:ZERO2W)

    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W, :PICO2, :PICO2, :PICO2].sort, @checkout.items.sort

    @checkout.remove(:PICO2)

    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W, :PICO2, :PICO2].sort, @checkout.items.sort

    2.times do
      @checkout.remove(:PICO2)
    end

    assert_equal [:ZERO2W, :ZERO2W, :ZERO2W].sort, @checkout.items.sort
  end

  def test_that_total_is_correctly_recalculated_when_items_are_added
    skip

    2.times do
      @checkout.add(:PICO2)
    end

    assert_equal 8.00, @checkout.total

    @checkout.add(:PICO2) # 3 in total now, so discount applies

    assert_equal 10.50, @checkout.total

    4.times do
      @checkout.add(:ZERO2W) # 30.00 with BOGOF
    end

    assert_equal 40.50, @checkout.total
  end

  def test_that_total_is_correctly_recalculated_when_items_are_removed
    skip

    3.times do
      @checkout.add(:PICO2) # Bulk discount applies
    end

    assert_equal 10.50, @checkout.total

    @checkout.remove(:PICO2) # Bulk discount no longer applies

    assert_equal 8.00, @checkout.total
  end
end