django - django tests response.request.user.is_authenticated() returning True after logout

Question

I am trying to write some tests for the authentication part of my application and I encountered a problem with checking if the user is logged in or not. Here's the code:

    client = Client()

    # user signup form
    response = client.post(signup_url, data={
        'email': "lorem@ipsum.pl",
        'password1': 'hunter2',
        'password2': 'hunter2',
    }, follow=True)

    # checking if the user is logged in
    with self.assertRaises(KeyError):
        client.session['_auth_user_id']

    self.assertEquals(len(mail.outbox), 1)
    url = find_verification_url(mail.outbox[0].body)
    response = client.get(url, follow=True)
    self.assertEqual(200, response.status_code)

    user = User.objects.get(email="lorem@ipsum.pl")

    self.assertEqual(client.session['_auth_user_id'], user.pk)

    # how to logout a user?
    force_logout()

    self.assertFalse(response.request.user.is_authenticated())

The user fills the form and clicks submit, then receives an email with a verification url. After he clicks the verification url in the email he's supposed to get directed to the site and authenticated. My questions is, what is a good way to find out if the user is authenticated or not? What is a preferred way to log out a user in this situation? I want to check that if the user is logged out and clicks the link the verification link second time it doesn't work. I tried some things like:

client.logout()

But unfortunately it seems to work once every two times even when I remove this line.

Thanks for any help!