add test to demonstrate issue with markdown extension parsing. adding mkd as an extension should not cause mkdn files to also be markdownified

test/test_generated_site.rb

@@ -14,7 +14,7 @@ class TestGeneratedSite < Test::Unit::TestCase
     end
 
     should "ensure post count is as expected" do
-      assert_equal 35, @site.posts.size
+      assert_equal 36, @site.posts.size
     end
 
     should "insert site.posts into the index" do

test/test_post.rb

@@ -562,6 +562,13 @@ class TestPost < Test::Unit::TestCase
       assert conv.kind_of? Jekyll::Converters::Markdown
     end
 
+    should "process .mkdn under text if it is not in the markdown config" do
+      @site.config['markdown_ext'] = 'markdown,mkd,md,text'
+      post = setup_post '2013-08-01-mkdn-extension.mkdn'
+      conv = post.converter
+      assert conv.kind_of? Jekyll::Converters::Identity
+    end
+
     should "process .text as textile under alternate configuration" do
       @site.config['textile_ext'] = 'textile,text'
       post = setup_post '2011-04-12-text-extension.text'