Polymer testing firebase

I'm trying to run some tests for registering to my app

suite('registering', function() {
   var userManager;
   setup(function() {
       userManager = fixture('UserManager');
       return userManager.register();
   }); // setup
});

The methods in userManager that i'm using are:

register: function() {
    return this._handleRegister().then(function(user) {
       return this._updateUserData(user);
     });
},

_updateUserData: function(user) {
    var updates = {};
    var uid = user.uid;
    var path = 'users/' + uid + '/';

    var meta = {
        publicData: false
    }
    var data = {
        name: '',
        image: '',
        team: '',
        email: ''
    }
    var history = {
        createdOn: firebase.database.ServerValue.TIMESTAMP
    }

    updates[path + 'meta'] = meta;
    updates[path + 'data'] = data;
    updates[path + 'history'] = history;

    return firebase.database().ref().update(updates);
},


_handleRegister: function() {
    return this.$.auth.signInAnonymously();
},

This works fine in my application but when executing the test it seems to go into a loop that perpetually increases RAM usage and sets CPU usage to near 100%

_handleRegister returns Promise non-null user

_updateUserData returns Promise null

Testing these methods individually work fine, both tests below pass

test('can i register a user', function() {
    return userManager._handleRegister().then(function(user) {
        expect(user.uid).to.be.a('string');
        console.log(userManager._user.uid);
        expect(userManager._user.uid).to.be.a('string');
        return userManager.signOut();
    });
});



test('can i update the user with user data', function() {
       return userManager._handleRegister().then(function(user) {
           return userManager._updateUserData(user);
       });
   });

Its when i combine them into one method register() and use it in the tests setup the error happens.

Whats the difference?