From 4f44249edf6becb34fd1d0ac633967cd4509da35 Mon Sep 17 00:00:00 2001
From: Hilary Holz <hilary@hholz.com>
Date: Thu, 20 Apr 2017 17:02:01 -0700
Subject: [PATCH 1/5] initial skeleton

---
 exercises/luhn/.meta/.version |  1 +
 exercises/luhn/example.tt     | 18 ++++++++++++++++++
 lib/luhn_cases.rb             | 11 +++++++++++
 3 files changed, 30 insertions(+)
 create mode 100644 exercises/luhn/.meta/.version
 create mode 100644 exercises/luhn/example.tt
 create mode 100644 lib/luhn_cases.rb

diff --git a/exercises/luhn/.meta/.version b/exercises/luhn/.meta/.version
new file mode 100644
index 0000000000..56a6051ca2
--- /dev/null
+++ b/exercises/luhn/.meta/.version
@@ -0,0 +1 @@
+1
\ No newline at end of file
diff --git a/exercises/luhn/example.tt b/exercises/luhn/example.tt
new file mode 100644
index 0000000000..469bb4eb34
--- /dev/null
+++ b/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 %>
+    assert_equal <%= test_case.expected %>, <%= test_case.work_load %>
+  end
+<% end %>
+<%= IO.read(XRUBY_LIB + '/bookkeeping.md') %>
+  def test_bookkeeping
+    skip
+    assert_equal <%= version %>, BookKeeping::VERSION
+  end
+end
diff --git a/lib/luhn_cases.rb b/lib/luhn_cases.rb
new file mode 100644
index 0000000000..88ba7da1dc
--- /dev/null
+++ b/lib/luhn_cases.rb
@@ -0,0 +1,11 @@
+require 'exercise_cases'
+
+class LuhnCase < OpenStruct
+  def name
+    'test_%s' % description.tr(' ', '_')
+  end
+
+  def skipped
+    index.zero? ? '# skip' : 'skip'
+  end
+end

From b5bbc00ca20b940fd3ea8650794c4ca18e1723cc Mon Sep 17 00:00:00 2001
From: Hilary J Holz <hilary@hholz.com>
Date: Thu, 20 Apr 2017 22:08:25 -0400
Subject: [PATCH 2/5] Generator for Luhn, with example solution

Cases and template seem to be very simple, and may be used in
documenting this process.
---
 exercises/luhn/.meta/.version |  2 +-
 exercises/luhn/example.rb     | 45 +++++++++---------
 exercises/luhn/example.tt     |  2 +-
 exercises/luhn/luhn_test.rb   | 87 ++++++++++++++++++++++++-----------
 lib/luhn_cases.rb             | 16 ++++++-
 5 files changed, 99 insertions(+), 53 deletions(-)

diff --git a/exercises/luhn/.meta/.version b/exercises/luhn/.meta/.version
index 56a6051ca2..d00491fd7e 100644
--- a/exercises/luhn/.meta/.version
+++ b/exercises/luhn/.meta/.version
@@ -1 +1 @@
-1
\ No newline at end of file
+1
diff --git a/exercises/luhn/example.rb b/exercises/luhn/example.rb
index 58e1242245..1405165d47 100644
--- a/exercises/luhn/example.rb
+++ b/exercises/luhn/example.rb
@@ -1,35 +1,34 @@
 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.
+      sum {|c, i| i.odd? ? DOUBLE[c.to_i] : c.to_i }
   end
 
   def valid?
-    checksum % 10 == 0
+    clean? && checksum_mod_10.zero?
+  end
+
+  def clean?
+    @string.match(/^\d{2,}$/)
   end
+
+  def checksum_mod_10
+    checksum % 10
+  end
+end
+module BookKeeping
+  VERSION = 1
 end
+
diff --git a/exercises/luhn/example.tt b/exercises/luhn/example.tt
index 469bb4eb34..b46731eae5 100644
--- a/exercises/luhn/example.tt
+++ b/exercises/luhn/example.tt
@@ -7,7 +7,7 @@ require_relative 'luhn'
 class LuhnTest < Minitest::Test<% test_cases.each do |test_case| %>
   def <%= test_case.name %>
     <%= test_case.skipped %>
-    assert_equal <%= test_case.expected %>, <%= test_case.work_load %>
+    <%= test_case.assertion %> <%= test_case.work_load %>
   end
 <% end %>
 <%= IO.read(XRUBY_LIB + '/bookkeeping.md') %>
diff --git a/exercises/luhn/luhn_test.rb b/exercises/luhn/luhn_test.rb
index 52d5538cc1..1b7828f669 100755
--- a/exercises/luhn/luhn_test.rb
+++ b/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
diff --git a/lib/luhn_cases.rb b/lib/luhn_cases.rb
index 88ba7da1dc..20915aad25 100644
--- a/lib/luhn_cases.rb
+++ b/lib/luhn_cases.rb
@@ -2,10 +2,24 @@
 
 class LuhnCase < OpenStruct
   def name
-    'test_%s' % description.tr(' ', '_')
+    'test_%s' % description.tr('- ', '__')
+  end
+
+  def work_load
+    %Q(Luhn.valid?("#{input}"))
   end
 
   def skipped
     index.zero? ? '# skip' : 'skip'
   end
+
+  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

From 45e2de53427e6d7837bc8dc34ccca440db77f4da Mon Sep 17 00:00:00 2001
From: Hilary Holz <hilary@hholz.com>
Date: Thu, 20 Apr 2017 23:30:09 -0700
Subject: [PATCH 3/5] update example.rb for ruby 2.1.2

---
 exercises/luhn/example.rb | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/exercises/luhn/example.rb b/exercises/luhn/example.rb
index 1405165d47..f53ac38d01 100644
--- a/exercises/luhn/example.rb
+++ b/exercises/luhn/example.rb
@@ -13,22 +13,18 @@ def initialize(string)
   def checksum
     @string.
       reverse.each_char.with_index.
-      sum {|c, i| i.odd? ? DOUBLE[c.to_i] : c.to_i }
+      reduce(0) {|sum, (c, i)| sum + (i.odd? ? DOUBLE[c.to_i] : c.to_i) }
   end
 
   def valid?
-    clean? && checksum_mod_10.zero?
+    clean? && (checksum % 10).zero?
   end
 
   def clean?
     @string.match(/^\d{2,}$/)
   end
-
-  def checksum_mod_10
-    checksum % 10
-  end
 end
+
 module BookKeeping
   VERSION = 1
 end
-

From 38f37161aa7f4ba45dfd674b8299334565d63296 Mon Sep 17 00:00:00 2001
From: Hilary Holz <hilary@hholz.com>
Date: Thu, 20 Apr 2017 23:57:11 -0700
Subject: [PATCH 4/5] simplify example.tt and luhn_cases.rb api

---
 exercises/luhn/example.tt | 2 +-
 lib/luhn_cases.rb         | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/exercises/luhn/example.tt b/exercises/luhn/example.tt
index b46731eae5..9a761d5d99 100644
--- a/exercises/luhn/example.tt
+++ b/exercises/luhn/example.tt
@@ -7,7 +7,7 @@ require_relative 'luhn'
 class LuhnTest < Minitest::Test<% test_cases.each do |test_case| %>
   def <%= test_case.name %>
     <%= test_case.skipped %>
-    <%= test_case.assertion %> <%= test_case.work_load %>
+    <%= test_case.work_load %>
   end
 <% end %>
 <%= IO.read(XRUBY_LIB + '/bookkeeping.md') %>
diff --git a/lib/luhn_cases.rb b/lib/luhn_cases.rb
index 20915aad25..991d08d2a7 100644
--- a/lib/luhn_cases.rb
+++ b/lib/luhn_cases.rb
@@ -6,13 +6,15 @@ def name
   end
 
   def work_load
-    %Q(Luhn.valid?("#{input}"))
+    %Q(#{assertion} Luhn.valid?("#{input}"))
   end
 
   def skipped
     index.zero? ? '# skip' : 'skip'
   end
 
+  private
+
   def assertion
     expected ? 'assert' : 'refute'
   end

From 9d8f722fe0b561de5c233996c96b10e4dfca7b14 Mon Sep 17 00:00:00 2001
From: Hilary Holz <hilary@hholz.com>
Date: Fri, 21 Apr 2017 00:25:32 -0700
Subject: [PATCH 5/5] requested changes

---
 exercises/luhn/example.tt | 2 +-
 lib/luhn_cases.rb         | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/exercises/luhn/example.tt b/exercises/luhn/example.tt
index 9a761d5d99..0770a41b04 100644
--- a/exercises/luhn/example.tt
+++ b/exercises/luhn/example.tt
@@ -7,7 +7,7 @@ require_relative 'luhn'
 class LuhnTest < Minitest::Test<% test_cases.each do |test_case| %>
   def <%= test_case.name %>
     <%= test_case.skipped %>
-    <%= test_case.work_load %>
+    <%= test_case.workload %>
   end
 <% end %>
 <%= IO.read(XRUBY_LIB + '/bookkeeping.md') %>
diff --git a/lib/luhn_cases.rb b/lib/luhn_cases.rb
index 991d08d2a7..df608b4e23 100644
--- a/lib/luhn_cases.rb
+++ b/lib/luhn_cases.rb
@@ -5,8 +5,8 @@ def name
     'test_%s' % description.tr('- ', '__')
   end
 
-  def work_load
-    %Q(#{assertion} Luhn.valid?("#{input}"))
+  def workload
+    %Q(#{assertion} Luhn.valid?(#{input.inspect}))
   end
 
   def skipped