Testing express.js app in own environment with dummy db

I've got the following structure for my web app

db.js:

mongoose = require('mongoose');
db = mongoose.createConnection("...");
playerSchema = new mongoose.Schema({
  // my schema stuff
});
exports.Player = db.model("player", playerSchema);

I have all my routes in an own file (route/index.js):

db = require('../db');

exports.createPlayer = function(req, res) {
  player = new db.Player();
  player.name = req.body.player_name;
  player.save(function(err) {
    if (err) {
      log(err);
    }
    res.redirect("/");
  });
};

app.js

routes = require('./routes');
app.post("/start", routes.createPlayer);

I test the app using mocha, should and supertest like the following example

should = require('should');
supertest = require('supertest');
app = require('../app');

describe("POST /start", function() {
  it("should redirect", function(done) {
    supertest(app)
    .post("/start")
    .send({
      player_name: "John Wayne"
    }).end(function(err, res) {
      should.not.exist(err);
      done();
    });
  });
});

It all works fine but I don't want to test against my production database. Does anyone know a smart way to use a dummy/different db just for testing? Maybe using a different environment? I'm kind of stuck!