code: function clean(test) {
    var err = test.err || {};
    if (err instanceof Error) {
      err = errorJSON(err);
    }
  
    return {
      title: test.title,
      fullTitle: test.fullTitle(),
      duration: test.duration,
      currentRetry: test.currentRetry(),
      err: cleanCycles(err)
    };
  }
docs: Return a plain-object representation of `test`
  free of cyclic properties etc.
  
  @private
  @param {Object} test
  @return {Object}