start-stop-daemon not working as expected

I can’t figure out why start-stop-daemon is not running the script below. What am I doing wrong? start-stop-daemon reports that it will start node when using the –test flag, but when I actually run the process isn’t started.

root@server:~# cat /var/www/a/app.js
var http = require("http")
var fs = require("fs")

fs.writeFileSync("app.pid", process.pid)

http.createServer(function(req, res)
{
    res.writeHead(200, {"Content-Type": "text/plain"})
    res.end("Test")
}).listen(3000)

console.log("App A is running, PID", process.pid)
root@server:~# node /var/www/a/app.js
App A is running, PID 18517
^Z
[1]+  Stopped                 node /var/www/a/app.js
root@server:~# pidof node
18517
root@server:~# kill -9 `pidof node`
root@server:~# fg
-su: fg: job has terminated
[1]+  Killed                  node /var/www/a/app.js
root@server:~# rm /var/www/a/app.pid
root@server:~# start-stop-daemon --start --pidfile /var/www/a/app.pid --chdir /var/www/a --chuid www-data:www-data --background --exec /opt/iojs/bin/node app.js --test
Would start /opt/iojs/bin/node app.js  (as user www-data[33], and group www-data[33]).
root@server:~# start-stop-daemon --start --pidfile /var/www/a/app.pid --chdir /var/www/a --chuid www-data:www-data --background --exec /opt/iojs/bin/node app.js
root@server:~# pidof node
root@server:~# start-stop-daemon --start --pidfile /var/www/a/app.pid --chdir /var/www/a --chuid www-data:www-data --background --exec app.js --test
Would start app.js  (as user www-data[33], and group www-data[33]).