Add tests for reverting to foreign versions.

test/functional/posts_controller_test.rb

@@ -127,6 +127,16 @@ class PostsControllerTest < ActionController::TestCase
         @post.reload
         assert_equal("aaaa", @post.tag_string)
       end
+
+      should "not allow reverting to a previous version of another post" do
+        @post2 = FactoryGirl.create(:post, :uploader_id => @user.id, :tag_string => "herp")
+
+        post :revert, { :id => @post.id, :version_id => @post2.versions.first.id }, {:user_id => @user.id}
+        @post.reload
+
+        assert_not_equal(@post.tag_string, @post2.tag_string)
+        assert_response :missing
+      end
     end
   end
 end