test_price.rb

require_relative 'check_out'
require 'minitest/autorun'

class TestPrice < Minitest::Test
  RULES = [
    ModPrice.new('A', 3, 50, 130),
    ModPrice.new('B', 2, 30, 45),
    FixedPrice.new('C', 20),
    FixedPrice.new('D', 15),
  ]

  def test_totals
    assert_equal(  0, price(""))
    assert_equal( 50, price("A"))
    assert_equal( 80, price("AB"))
    assert_equal(115, price("CDBA"))

    assert_equal(100, price("AA"))
    assert_equal(130, price("AAA"))
    assert_equal(180, price("AAAA"))
    assert_equal(230, price("AAAAA"))
    assert_equal(260, price("AAAAAA"))

    assert_equal(160, price("AAAB"))
    assert_equal(175, price("AAABB"))
    assert_equal(190, price("AAABBD"))
    assert_equal(190, price("DABABA"))
  end

  def test_incremental
    co = CheckOut.new(RULES)
    assert_equal(  0, co.total)
    co.scan("A");  assert_equal( 50, co.total)
    co.scan("B");  assert_equal( 80, co.total)
    co.scan("A");  assert_equal(130, co.total)
    co.scan("A");  assert_equal(160, co.total)
    co.scan("B");  assert_equal(175, co.total)
  end

  private

  def price(goods)
    co = CheckOut.new(RULES)
    goods.split(//).each { |item| co.scan(item) }
    co.total
  end
end