Testing an update hook that updates fields?
Yes, very quickly. You already have part of the code. Since you have already loaded the node via the entity_metadata_wrapper() you have all of the information at your finger tips.

An example is this in your hook_update_N()

foreach ($node_ids as $node_id) {
    try {
      $node_wrapper = entity_metadata_wrapper('node', $node_id);
      $node_wrapper-&gt;field_new_field-&gt;set($node_wrapper-&gt;field_old_field[0]-&gt;value());
      $node_wrapper-&gt;save();
      if ($node_wrapper-&gt;field_new_field-&gt;value() == $node_wrapper-&gt;field_old_field-&gt;value()){
        print_r('Success. Old field data is in new field data');
      }
    }
    catch (Exception $e) {
      watchdog('mymodule', 'Problem with node @node_id', array('@node_id' =&gt; $node_id), WATCHDOG_ERROR);
    }
    $sandbox['progress']++;
  }


I added a comparison of the old field data and the new field data. If it is the same, it will print 'Success. Old field data is in new field data' in the console of Travis-CI. You can do this for any entity. You can use print_r() to output data that you can see in Travis-CI's console. I do this for troubleshooting my test scripts when I may be using a new test method I have never used before and I want to see what Drupal is giving me. Most of the modules I maintain on D.O are tested with Travis-CI.