Simply return any custom HTTP code by supplying the url param ?code=302

app.js

var url  = require('url');
var http = require('http');
var querystring = require('querystring');

// Example usage: curl -I http://localhost:1337/?code=500
http.createServer(function (req, res) {
  var purl = url.parse(req.url).query;
  var qs = querystring.parse(purl);

  var status_code = qs.code || 200;

  res.writeHead(status_code, {'Content-Type': 'text/plain'});
  res.end('Hello Status code: ' + status_code + '\n');

}).listen(process.env.PORT || 1337);
console.log('Server running at http://127.0.0.1:1337/');