Added array_to_sentence_string filter

lib/jekyll/filters.rb

@@ -20,5 +20,20 @@ module Jekyll
     def number_of_words(input)
       input.split.length
     end
+    
+    def array_to_sentence_string(array)
+      connector = "and"
+      case array.length
+      when 0
+        ""
+      when 1
+        array[0].to_s
+      when 2
+        "#{array[0]} #{connector} #{array[1]}"
+      else
+        "#{array[0...-1].join(', ')}, #{connector} #{array[-1]}"
+      end
+    end
+
   end  
 end

test/test_filters.rb

@@ -0,0 +1,32 @@
+require File.dirname(__FILE__) + '/helper'
+
+class TestSite < Test::Unit::TestCase
+  
+  class JekyllFilter
+    include Jekyll::Filters
+  end
+  
+  def setup
+    @filter = JekyllFilter.new
+  end
+
+  def test_array_to_sentence_string_with_no_args
+    assert_equal "", @filter.array_to_sentence_string([])
+  end
+
+  def test_array_to_sentence_string_with_one_arg
+    assert_equal "1", @filter.array_to_sentence_string([1])
+    assert_equal "chunky", @filter.array_to_sentence_string(["chunky"])
+  end
+  
+  def test_array_to_sentence_string_with_two_args
+    assert_equal "1 and 2", @filter.array_to_sentence_string([1, 2])
+    assert_equal "chunky and bacon", @filter.array_to_sentence_string(["chunky", "bacon"])
+  end
+  
+  def test_array_to_sentence_string_with_multiple_args
+    assert_equal "1, 2, 3, and 4", @filter.array_to_sentence_string([1, 2, 3, 4])
+    assert_equal "chunky, bacon, bits, and pieces", @filter.array_to_sentence_string(["chunky", "bacon", "bits", "pieces"])
+  end
+  
+end