Merge pull request #170 from exercism/10_forces_implementation_concerns

No longer drives the solution

largest-series-product/example.rb

@@ -3,34 +3,43 @@
 class Series
   attr_reader :digits
   def initialize(numeric_string)
-    @digits = convert_to_digits(numeric_string)
+    @digits = numeric_string
   end
 
   def largest_product(length)
-    fail ArgumentError.new('Not enough digits') if length > digits.length
-    products = []
-    slices(length).each do |slice|
-      products << slice.inject(1) do |product, n|
-        product * n
-      end
-    end
-    products.sort.last
+    @length = length
+    validate_length
+    return 1 if @digits.empty?
+    collection_of_digits
+    select_max { reduce_to_product  { validate  { separate } } }
+  end
+
+  private
+
+  def validate_length
+    @length > digits.length and
+      fail(ArgumentError.new 'Not enough digits')
   end
 
-  def slices(length)
-    result = []
-    i = -1
-    begin
-      i += 1
-      i2 = i + length - 1
-      result << digits[i..i2]
-    end while i2 < digits.size - 1
-    result
+  def validate
+    yield.take_while { |array| array.size == @length }
   end
 
-  private
+  def reduce_to_product
+    yield.map { |array| array.inject(1, :*) }
+  end
+
+  def select_max
+    yield.max
+  end
+
+  def separate
+    digits.map.with_index do |_, index|
+      digits[index, @length]
+    end
+  end
 
-  def convert_to_digits(s)
-    s.chars.to_a.map(&:to_i)
+  def collection_of_digits
+    @digits = digits.chars.map(&:to_i)
   end
 end

largest-series-product/largest_series_product_test.rb

@@ -5,68 +5,10 @@
 
 # Rubocop directives
 # rubocop:disable Lint/ParenthesesAsGroupedExpression
+# rubocop:disable Style/AlignParameters:
 #
 class Seriestest < Minitest::Test
-  def test_digits
-    assert_equal (0..9).to_a, Series.new('0123456789').digits
-  end
-
-  def test_same_digits_reversed
-    skip
-    assert_equal (0..9).to_a.reverse, Series.new('9876543210').digits
-  end
-
-  def test_fewer_digits
-    skip
-    assert_equal (4..8).to_a.reverse, Series.new('87654').digits
-  end
-
-  def test_some_other_digits
-    skip
-    assert_equal [9, 3, 6, 9, 2, 3, 4, 6, 8], Series.new('936923468').digits
-  end
-
-  def test_slices_of_zero
-    skip
-    assert_equal [], Series.new('').digits
-  end
-
-  def test_slices_of_2
-    skip
-    series = Series.new('01234')
-    expected = [[0, 1], [1, 2], [2, 3], [3, 4]]
-    assert_equal expected, series.slices(2)
-  end
-
-  def test_other_slices_of_2
-    skip
-    series = Series.new('98273463')
-    expected = [[9, 8], [8, 2], [2, 7], [7, 3], [3, 4], [4, 6], [6, 3]]
-    assert_equal expected, series.slices(2)
-  end
-
-  def test_slices_of_3
-    skip
-    series = Series.new('01234')
-    expected = [[0, 1, 2], [1, 2, 3], [2, 3, 4]]
-    assert_equal expected, series.slices(3)
-  end
-
-  def test_other_slices_of_3
-    skip
-    series = Series.new('982347')
-    expected = [[9, 8, 2], [8, 2, 3], [2, 3, 4], [3, 4, 7]]
-    assert_equal expected, series.slices(3)
-  end
-
-  def test_largest_product_of_2
-    skip
-    series = Series.new('0123456789')
-    assert_equal 72, series.largest_product(2)
-  end
-
   def test_largest_product_of_a_tiny_number
-    skip
     series = Series.new('12')
     assert_equal 2, series.largest_product(2)
   end
@@ -77,10 +19,18 @@ def test_another_tiny_number
     assert_equal 9, series.largest_product(2)
   end
 
+  def test_largest_product_of_2
+    skip
+    series = Series.new('0123456789')
+    assert_equal 72, series.largest_product(2),
+      'Largest product of all sets of 2 result from 8 and 9'
+  end
+
   def test_largest_product_of_2_shuffled
     skip
     series = Series.new('576802143')
-    assert_equal 48, series.largest_product(2)
+    assert_equal 48, series.largest_product(2),
+      'Largest product of all sets of 2 result from 6 and 8'
   end
 
   def test_largest_product_of_3
@@ -118,7 +68,8 @@ def test_some_other_big_number
   def test_identity
     skip
     series = Series.new('')
-    assert_equal 1, series.largest_product(0)
+    assert_equal 1, series.largest_product(0),
+      'Identity of an empty group is 1'
   end
 
   def test_slices_bigger_than_number