under-the-hood of test runners: yargs.js

// lib cli/cli.js main()
  const argv = process.argv.slice(2);
  // lib/cli/options loadOptions()
  var args = yargsParser.detailed(argv).argv;
  args._ = Array.from(new Set(args._));

  yargs()
    .scriptName("our_mocha")
    .command(commands.run)
    .fail((msg, err, yargs) => {
      yargs.showHelp();
      const message = msg || err.message;
      console.error(`\nERROR: ${message}`);
      process.exit(1);
    })
    .help("help", "Show usage information & exit")
    .version("version", "Show version number & exit", "1.0")
    .epilog("Mocha Resources: ...")
    .config(args)
    .parse(args._);