function clean(test) {
    var err = test.err || {};
    if (err instanceof Error) {
      err = errorJSON(err);
    }

    return {
      title: test.title,
      fullTitle: test.fullTitle(),
      file: test.file,
      duration: test.duration,
      currentRetry: test.currentRetry(),
      speed: test.speed,
      err: cleanCycles(err)
    };
  }
Return a plain-object representation of `test`
free of cyclic properties etc.

@private
@param {Object} test
@return {Object}