code: async function compareString (filename, expectedContents) {
    try {
      const actualContents = await fs.readFile(filename, { encoding: 'utf8' })
      return actualContents !== expectedContents
    } catch (err) {
      return handleError(err)
    }
  }
docs: Compares a string with a file contents. Returns true, if they differ or the file does not exist.
  @param {string} filename the file name
  @param {string} expectedContents the file contents
  @returns {Promise<boolean>|boolean}
  @private