package.json

{
  "name": "test_uuid",
  "version": "1.0.0",
  "description": "Test UIDs in Firebase",
  "scripts": {
    "test": "node ./test.js"
  },
  "devDependencies": {
    "firebase": "^2.2.9",
    "firebase-token-generator": "^2.0.0",
    "node-uuid": "^1.4.3"
  }
}

test.js

var Firebase = require('firebase');
var uuid = require('node-uuid');

var FirebaseTokenGenerator = require("firebase-token-generator");
var tokenGenerator = new FirebaseTokenGenerator("<YOUR_FIREBASE_SECRET>");
var token = tokenGenerator.createToken({uid: uuid.v4(), provider: 'password'}, {debug: true});

var ref = new Firebase('https://<YOUR_FIREBASE_APP>.firebaseio.com');
ref.authWithCustomToken(token, function(err, user) {
  if( err ) { throw err; }
  else {
    /** run your tests here **/
  }
});