Testing authentication on nodejs app with facebook test users

I'm testing the Facebook authentication on my nodejs webapp and I'm banging my head against the customization of the content of the test-user's token.

I'm first creating a Facebook test-user with my facebook_app_id.
It gives me an id, an email, a token... And I'm using that last one to create a user on my webapp. This works without problem. There's an 'email' key in that one!

The real test starts here. I'm now trying to log using my Facebook test-user access token. The test fails because there's actually no key 'email' in the access token (which I'm using internally to identify the user).

I've been searching throw the GraphApi documentation to see if there was any way to get that information in the token (like permissions?) in vain.

Any idea? Am I doing something wrong here?