diff --git a/test/exemplars/attachment_exemplar.rb b/test/exemplars/attachment_exemplar.rb
index 8100fe906..4baaf530f 100644
--- a/test/exemplars/attachment_exemplar.rb
+++ b/test/exemplars/attachment_exemplar.rb
@@ -12,6 +12,6 @@ class Attachment < ActiveRecord::Base
   end
 
   def self.generate_file
-    @file = mock_file
+    @file = ActiveSupport::TestCase.mock_file
   end
 end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index dc04fa82d..9a2761021 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -63,7 +63,7 @@ class ActiveSupport::TestCase
   end
 
   # Mock out a file
-  def mock_file
+  def self.mock_file
     file = 'a_file.png'
     file.stubs(:size).returns(32)
     file.stubs(:original_filename).returns('a_file.png')
@@ -71,7 +71,11 @@ class ActiveSupport::TestCase
     file.stubs(:read).returns(false)
     file
   end
-  
+
+  def mock_file
+    self.class.mock_file
+  end
+
   # Use a temporary directory for attachment related tests
   def set_tmp_attachments_directory
     Dir.mkdir "#{RAILS_ROOT}/tmp/test" unless File.directory?("#{RAILS_ROOT}/tmp/test")