Luhn with generator (#559)

Test generator for Luhn, with example solution

exercises/luhn/.meta/.version

@@ -0,0 +1 @@
+1

exercises/luhn/example.rb

@@ -1,35 +1,30 @@
 class Luhn
-  def self.create(number)
-    test_number = number * 10
-    luhn = Luhn.new(test_number)
-    return test_number if luhn.valid?
-    test_number + 10 - (luhn.checksum % 10)
-  end
+  DOUBLE = [0, 2, 4, 6, 8, 1, 3, 5, 7, 9]
+  DOUBLE.freeze
 
-  attr_reader :number
-  def initialize(number)
-    @number = number
+  def self.valid?(string)
+    Luhn.new(string).valid?
   end
 
-  def addends
-    numbers = []
-    number.to_s.reverse.split('').map(&:to_i).each_with_index do |n, i|
-      if i % 2 == 0
-        numbers << n
-      else
-        value = n * 2
-        value -= 9 if value > 9
-        numbers << value
-      end
-    end
-    numbers.reverse
+  def initialize(string)
+    @string = string.tr(' ', '')
   end
 
   def checksum
-    addends.inject(0, :+)
+    @string.
+      reverse.each_char.with_index.
+      reduce(0) {|sum, (c, i)| sum + (i.odd? ? DOUBLE[c.to_i] : c.to_i) }
   end
 
   def valid?
-    checksum % 10 == 0
+    clean? && (checksum % 10).zero?
+  end
+
+  def clean?
+    @string.match(/^\d{2,}$/)
   end
 end
+
+module BookKeeping
+  VERSION = 1
+end

exercises/luhn/example.tt

@@ -0,0 +1,18 @@
+#!/usr/bin/env ruby
+gem 'minitest', '>= 5.0.0'
+require 'minitest/autorun'
+require_relative 'luhn'
+
+# Common test data version: <%= abbreviated_commit_hash %>
+class LuhnTest < Minitest::Test<% test_cases.each do |test_case| %>
+  def <%= test_case.name %>
+    <%= test_case.skipped %>
+    <%= test_case.workload %>
+  end
+<% end %>
+<%= IO.read(XRUBY_LIB + '/bookkeeping.md') %>
+  def test_bookkeeping
+    skip
+    assert_equal <%= version %>, BookKeeping::VERSION
+  end
+end

exercises/luhn/luhn_test.rb

@@ -3,57 +3,90 @@
 require 'minitest/autorun'
 require_relative 'luhn'
 
+# Common test data version: c826372
 class LuhnTest < Minitest::Test
-  def test_addends
-    luhn = Luhn.new(12_121)
-    assert_equal [1, 4, 1, 4, 1], luhn.addends
+  def test_single_digit_strings_can_not_be_valid
+    # skip
+    refute Luhn.valid?("1")
   end
 
-  def test_too_large_addend
+  def test_A_single_zero_is_invalid
     skip
-    luhn = Luhn.new(8631)
-    assert_equal [7, 6, 6, 1], luhn.addends
+    refute Luhn.valid?("0")
   end
 
-  def test_checksum
+  def test_a_simple_valid_SIN_that_remains_valid_if_reversed
     skip
-    luhn = Luhn.new(4913)
-    assert_equal 22, luhn.checksum
+    assert Luhn.valid?("059")
   end
 
-  def test_checksum_again
+  def test_a_simple_valid_SIN_that_becomes_invalid_if_reversed
     skip
-    luhn = Luhn.new(201_773)
-    assert_equal 21, luhn.checksum
+    assert Luhn.valid?("59")
   end
 
-  def test_invalid_number
+  def test_a_valid_Canadian_SIN
     skip
-    luhn = Luhn.new(738)
-    refute luhn.valid?
+    assert Luhn.valid?("055 444 285")
   end
 
-  def test_valid_number
+  def test_invalid_Canadian_SIN
     skip
-    luhn = Luhn.new(8_739_567)
-    assert luhn.valid?
+    refute Luhn.valid?("055 444 286")
   end
 
-  def test_create_valid_number
+  def test_invalid_credit_card
     skip
-    number = Luhn.create(123)
-    assert_equal 1230, number
+    refute Luhn.valid?("8273 1232 7352 0569")
   end
 
-  def test_create_other_valid_number
+  def test_valid_strings_with_a_non_digit_included_become_invalid
     skip
-    number = Luhn.create(873_956)
-    assert_equal 8_739_567, number
+    refute Luhn.valid?("055a 444 285")
   end
 
-  def test_create_yet_another_valid_number
+  def test_valid_strings_with_punctuation_included_become_invalid
     skip
-    number = Luhn.create(837_263_756)
-    assert_equal 8_372_637_564, number
+    refute Luhn.valid?("055-444-285")
+  end
+
+  def test_valid_strings_with_symbols_included_become_invalid
+    skip
+    refute Luhn.valid?("055£ 444$ 285")
+  end
+
+  def test_single_zero_with_space_is_invalid
+    skip
+    refute Luhn.valid?(" 0")
+  end
+
+  def test_more_than_a_single_zero_is_valid
+    skip
+    assert Luhn.valid?("0000 0")
+  end
+
+  def test_input_digit_9_is_correctly_converted_to_output_digit_9
+    skip
+    assert Luhn.valid?("091")
+  end
+  # Problems in exercism evolve over time, as we find better ways to ask
+  # questions.
+  # The version number refers to the version of the problem you solved,
+  # not your solution.
+  #
+  # Define a constant named VERSION inside of the top level BookKeeping
+  # module, which may be placed near the end of your file.
+  #
+  # In your file, it will look like this:
+  #
+  # module BookKeeping
+  #   VERSION = 1 # Where the version number matches the one in the test.
+  # end
+  #
+  # If you are curious, read more about constants on RubyDoc:
+  # http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html
+  def test_bookkeeping
+    skip
+    assert_equal 1, BookKeeping::VERSION
   end
 end

lib/luhn_cases.rb

@@ -0,0 +1,27 @@
+require 'exercise_cases'
+
+class LuhnCase < OpenStruct
+  def name
+    'test_%s' % description.tr('- ', '__')
+  end
+
+  def workload
+    %Q(#{assertion} Luhn.valid?(#{input.inspect}))
+  end
+
+  def skipped
+    index.zero? ? '# skip' : 'skip'
+  end
+
+  private
+
+  def assertion
+    expected ? 'assert' : 'refute'
+  end
+end
+
+LuhnCases = proc do |data|
+  JSON.parse(data)['cases'].map.with_index do |row, i|
+    LuhnCase.new(row.merge('index' => i))
+  end
+end