Jest: Difference betwen –runInBand and –maxWorkers 1

There is no difference. Here’s the method where it gets read from the args object:

export default function getMaxWorkers(argv: Argv): number {
  if (argv.runInBand) {
    return 1;
  } else if (argv.maxWorkers) {
    return parseInt(argv.maxWorkers, 10);
  } else {
    const cpus = os.cpus().length;
    return Math.max(argv.watch ? Math.floor(cpus / 2) : cpus - 1, 1);
  }
}

original source code on github