function clean(test) {
    return {
      title: test.title,
      fullTitle: test.fullTitle(),
      file: test.file,
      duration: test.duration,
      currentRetry: test.currentRetry(),
      speed: test.speed
    };
  }
Returns an object literal representation of `test`
free of cyclic properties, etc.

@private
@param {Test} test - Instance used as data source.
@return {Object} object containing pared-down test instance data