node/test/parallel/test-child-process-spawnsync-env.js

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

if (process.argv[2] === 'child') {
  console.log(process.env.foo);
} else {
  const expected = 'bar';
  const child = cp.spawnSync(process.execPath, [__filename, 'child'], {
    env: Object.assign(process.env, { foo: expected })
  });

  assert.strictEqual(child.stdout.toString().trim(), expected);
}