node/test/parallel/test-force-repl-with-eval.js

'use strict';
require('../common');
const assert = require('assert');
const spawn = require('child_process').spawn;

// spawn a node child process in "interactive" mode (force the repl) and eval
const cp = spawn(process.execPath, ['-i', '-e', 'console.log("42")']);
let gotToEnd = false;

cp.stdout.setEncoding('utf8');

let output = '';
cp.stdout.on('data', function(b) {
  output += b;
  if (output === '> 42\n') {
    gotToEnd = true;
    cp.kill();
  }
});

process.on('exit', function() {
  assert(gotToEnd);
});