adding missing tests

test/fixtures/learning_object/attachments.yml

+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+one:
+  name: MyString
+  link: MyString
+  retrieve_link: MyString
+  description: MyText
+  format: MyString
+  mime_type: MyString
+  size: 1
+  bundle_name: MyString
+  learning_object_id: 
+
+two:
+  name: MyString
+  link: MyString
+  retrieve_link: MyString
+  description: MyText
+  format: MyString
+  mime_type: MyString
+  size: 1
+  bundle_name: MyString
+  learning_object_id: 

test/models/learning_object/attachment_test.rb

+require 'test_helper'
+
+class LearningObject::AttachmentTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end