ruby-checkout/tests.rb

require "minitest/autorun"

require "./checkout.rb"

class TestCheckout < Minitest::Test
  def setup
    @checkout = Checkout.new
  end

  def test_that_unknown_items_cannot_be_added
    assert_raises Checkout::InvalidItem do
      @checkout.add(:foo)
    end
  end

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

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

    assert_equal [:PI5, :ZERO2W, :PICO2].sort, @checkout.items.sort
  end

  def test_that_total_is_the_sum_of_all_items_when_no_discounts_apply
    @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

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

    refute_empty @checkout.items

    @checkout.clear

    assert_empty @checkout.items

  end

  # Discounts

  def test_that_bogof_applied
    4.times do
      @checkout.add(:ZERO2W) # Should remove 2 Zeros
    end

    assert_equal 30.00, @checkout.total
  end

  def test_that_bogof_applied_with_odd_number
    5.times do
      @checkout.add(:ZERO2W) # Should still remove 2 Zeros, 5th is full price
    end

    assert_equal 45.00, @checkout.total
  end

  def test_that_price_is_reduced_for_3_picos
    3.times do
      @checkout.add(:PICO2) # 3.50 * 3 = 10.50
    end

    assert_equal 10.50, @checkout.total
  end

  def test_that_price_is_reduced_for_more_than_3_picos
    4.times do
      @checkout.add(:PICO2) # 3.50 * 4 = 14
    end

    assert_equal 14.00, @checkout.total
  end

  def test_that_price_is_not_reduced_for_less_than_3_picos
    2.times do
      @checkout.add(:PICO2) # 4.00 * 2 = 8
    end

    assert_equal 8.00, @checkout.total
  end

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

    3.times do
      @checkout.add(:PICO2) # 10.50 with bulk discount
    end

    assert_equal (30.00 + 10.50), @checkout.total
  end

  # Item removal

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

    assert_equal [:PICO2], @checkout.items
  end

  def test_that_items_are_removed_one_by_one
    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
    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
    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