diff --git a/test/helper.rb b/test/helper.rb
index f4bdcf19..51194f56 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -28,17 +28,21 @@ class Test::Unit::TestCase
   include RR::Adapters::TestUnit
 
   def dest_dir(*subdirs)
-    File.join(File.dirname(__FILE__), 'dest', *subdirs)
+    test_dir('dest', *subdirs)
   end
 
   def source_dir(*subdirs)
-    File.join(File.dirname(__FILE__), 'source', *subdirs)
+    test_dir('source', *subdirs)
   end
 
   def clear_dest
     FileUtils.rm_rf(dest_dir)
   end
 
+  def test_dir(*subdirs)
+    File.join(File.dirname(__FILE__), *subdirs)
+  end
+
   def capture_stdout
     $old_stdout = $stdout
     $stdout = StringIO.new