RSpec version of the tests for Kata 09

check_out_spec.rb

# This is a reimplementation of the tests of this kata:
# http://codekata.com/kata/kata09-back-to-the-checkout/
# Original implementation by Dave Thomas

RSpec.describe CheckOut do
  # Item   Unit      Special
  #        Price     Price
  # --------------------------
  #  A     50       3 for 130
  #  B     30       2 for 45
  #  C     20
  #  D     15
  let(:rules) { } # Define rules here!

  it 'incremential scanning on the same bill' do
    checkout = CheckOut.new(rules)

    expect(checkout.total).to eq(0)

    checkout.scan('A')
    expect(checkout.total).to eq(50)

    checkout.scan('B')
    expect(checkout.total).to eq(80)

    checkout.scan('A')
    expect(checkout.total).to eq(130)

    checkout.scan('A')
    expect(checkout.total).to eq(160)

    checkout.scan('B')
    expect(checkout.total).to eq(175)
  end

  def total_of(items)
    checkout = CheckOut.new(rules)
    items.each do |item|
      checkout.scan(item)
    end
    checkout.total
  end

  it 'checking total of separate bills' do
    expect(total_of([])).to eq(0)
    expect(total_of(%w(A))).to eq(50)
    expect(total_of(%w(A B))).to eq(80)
    expect(total_of(%w(C D B A))).to eq(115)

    expect(total_of(%w(A A))).to eq(100)
    expect(total_of(%w(A A A))).to eq(130)
    expect(total_of(%w(A A A A))).to eq(180)
    expect(total_of(%w(A A A A A))).to eq(230)
    expect(total_of(%w(A A A A A A))).to eq(260)

    expect(total_of(%w(A A A B))).to eq(160)
    expect(total_of(%w(A A A B B))).to eq(175)
    expect(total_of(%w(A A A B B D))).to eq(190)
    expect(total_of(%w(D A B A B A))).to eq(190)
  end
end