public function test_changing_empty_attribute_value_tracks_change()
 {
     $event = new Event();
     $event->description = "The most fun";
     $changes = $event->changes();
     $this->assert_true(array_key_exists("description", $changes));
     $this->assert_equals("", $changes['description'][0]);
     $this->assert_equals("The most fun", $changes['description'][1]);
 }