testing facebook app with mocha

I'm developing a node.js app with Facebook login, I'm trying to do unit and integration tests with mocha. So in a function I have this code in order to login:

exports.loginFacebook = function (done){
request({uri:"https://graph.facebook.com//oauth/access_token?client_id={app-id}&client_secret={app-secret}&grant_type=client_credentials",
    method: "GET",
        timeout: reqOpts.timeout}, 
    function(err, res, body) {
    if(err){
        throw err;
    }
    else{
        uri2 = "https://graph.facebook.com/APP_ID/accounts/test-users?"+String(body);
        request({uri:uri2,
            method: "GET",
                timeout: reqOpts.timeout},
         function(err, res, body) {
            if(err){
                throw err;
            }
            else{
                login_url = JSON.parse(body).data[0].login_url
                console.log(login_url);
                request({uri:login_url,
                    method: "GET",
                    timeout: reqOpts.timeout},
                 function(err, res, body) {
                    if(err){
                        throw err;
                    }
                    else{
                          request('http://localhost:4004/auth/facebook', reqOpts, function(err, res, body2) {
                        //console.log(res.statusCode)
                        //console.log(err)
                        done()  
                      });   
                    }
                }); 
            }
        });
    }
});
};

Basically I call Facebook API to get the access token, then I list my testing users and I finally I login with the first one. Problem: when I call the login_url, Facebook redirects to this webpage: http://i.imgur.com/V6NzuMi.jpg ("update your browser"), so I'm not able to do a correct login.

Any ideas how to solve this?

thanks!