Luhn_test

credit_check.rb

class CreditCheck
  def validate(digits)
    if digits.empty?
      false
    else
      chars = digits.chars
      numbers = []
      chars.each {|char| numbers << char.to_i}

      numbers.reverse!

      multiplied_values = []
      count = 1
      numbers.each do |num|
        if count % 2 == 0
          multiplied_values << numbers * 2
        else
          multiplied_values << numbers
        end
        count = count + 1
      end

      doubled = []
      multiplied_values.map do |num|
        if num > 9
          doubled << num -9
        else
          doubled << num
        end
      end

      summed_up = 0
      doubled.each {|num| summed_up += num}

      validity = sum % 10 == 0

      if valid
        puts "The number is valid!"
      else
        puts "The number is invalid!"
      end
    end
  end

end

test_card = CreditCheck.new
test_card.validate('5541808923795240')

credit_check_test.rb

require 'minitest/autorun'
require 'minitest/pride'
require_relative 'credit_check'

class CreditCheckTest < Minitest::Test
  def test_credit_check_exists
    checker = CreditCheck.new
    assert checker
  end

  def test_empty_string_is_invalid
    checker = CreditCheck.new
    result = checker.validate("")
    assert_equal false, result
  end

  def test_zero_is_valid
    checker = CreditCheck.new
    result = checker.validate("0")
    assert_equal true, result
  end

  def test_it_returns_false_for_digits_not_divisible_by_ten
    checker = CreditCheck.new
    result = checker.validate("1")
    assert_equal false, result
  end

  def test_larger_digits_are_true_if_divisible_by_ten
    checker = CreditCheck.new
    result = checker.validate("42")
    assert_equal true, result
  end

  def test_longer_digits_return_true_as_long_as_divisible
    checker = CreditCheck.new
    result = checker.validate("42424242424242")
    assert_equal true, result
  end

  def test_numbers_not_divisible_return_false
    checker = CreditCheck.new
    result = checker.validate("58")
    assert_equal false, result
  end

  def test_actual_card_numbers
    checker = CreditCheck.new
    result = checker.validate('5541808923795240')
    assert_equal true, result
    result = checker.validate('4024007136512380')
    assert_equal true, result
  end

  def test_actual_card_numbers_return_false
    skip
    checker = CreditCheck.new
    result = checker.validate('5541801923795240')
    assert_equal false, result
    result = checker.validate('6011797668868728')
    assert_equal false, result
  end

end