cleo coding challenge

change_calculator.rb

# frozen_string_literal: true

class ChangeCalculator
  COINS = { 200 => '£2', 100 => '£1', 50 => '50p', 20 => '20p', 10 => '10p', 5 => '5p', 2 => '2p', 1 => '1p' }.freeze

  def self.calculate(amount)
    new(amount).calculate
  end

  def initialize(amount)
    @amount = (amount * 100).to_i
    @change = {}
  end

  def calculate
    COINS.keys.each do |coin|
      result = @amount / coin
      if result >= 1
        @change[COINS[coin]] = result.to_int
        @amount -= (result.to_int * coin)
      end
    end

    @change
  end
end

change_calculator_spec.rb

# frozen_string_literal: true

require 'change_calculator'

RSpec.describe ChangeCalculator do
  context 'change calculator' do
    it 'returns right change for 2.12' do
      expect(ChangeCalculator.calculate(2.12)).to eq({ '£2' => 1, '10p' => 1, '2p' => 1 })
    end
    it 'returns right change for 2.00' do
      expect(ChangeCalculator.calculate(2.00)).to eq({ '£2' => 1 })
    end

    it 'returns right change for 4.00' do
      expect(ChangeCalculator.calculate(4.00)).to eq({ '£2' => 2 })
    end

    it 'returns right change for 3.26' do
      expect(ChangeCalculator.calculate(3.26)).to eq({ '1p' => 1, '20p' => 1, '5p' => 1, '£1' => 1, '£2' => 1 })
    end
  end
end