child.js

var s = '';
for (var i = 0; i < 1E5; ++i) s += 'あ';
process.send(s);

parent.jp

var assert = require('assert');
var child = require('child_process').fork(__dirname + '/child.js');
child.on('message', function(s) {
  for (var i = 0, len = s.length; i < len; ++i)
    assert.equal(s[i], 'あ');
  child.kill();
});

result

$ node -v
v0.8.22
$ node parent.js 

assert.js:102
  throw new assert.AssertionError({
        ^
AssertionError: "�" == "あ"
    at ChildProcess.<anonymous> (/tmp/parent.js:5:12)
    at ChildProcess.EventEmitter.emit (events.js:99:17)
    at handleMessage (child_process.js:273:12)
    at Pipe.channel.onread (child_process.js:293:9)