function test(filename, tags) {
  if (Array.isArray(tags) === true) {
    return Promise.resolve(true);
  }
  return Promise.reject({
    level: 'ERROR',
    filename: filename,
    message: `Common tags file must be an array, was ${typeof tags}`,
  });
}
Tests and validates a commonTags.json file.
  Note: The returned promise always resolves, it will never reject.

@param {string} filename The name of the file to be tested.
@param {Object} tags The parsed contents of the tags file.
@return {Promise} A promise with the result of the test.