node/test/parallel/test-cluster-disconnect-before-exit.js

'use strict';
const common = require('../common');
const cluster = require('cluster');

if (cluster.isMaster) {
  const worker = cluster.fork().on('online', common.mustCall(disconnect));

  function disconnect() {
    worker.disconnect();
    // The worker remains in cluster.workers until both disconnect AND exit.
    // Disconnect is supposed to disconnect all workers, but not workers that
    // are already disconnected, since calling disconnect() on an already
    // disconnected worker would error.
    worker.on('disconnect', common.mustCall(cluster.disconnect));
  }
}