Django test login module can't be verified?

I want test login redirect, but I use client post username and password, Login-authenticate failed, I adjusted for a long time. I don't know why!

view:

def index(request, **kwargs):

    username = kwargs.get('username', 'anyone')
    return render(request, "index.html", {'username': username})

def login(request):

    """user sign in"""
    if request.method == "GET":
        form = LoginForm()
        return render(request, "login.html", {'uf': form})
    else:
        form = LoginForm(request.POST)
        if form.is_valid():
            username = request.POST.get("username")
            password = request.POST.get("password")
            user = auth.authenticate(username=username, password=password)
            if user is not None and user.is_active:
                auth.login(request, user)
                request.session['uid'] = user.id
                return render(request, 'index.html', {'username': username})
            else:
                return render(request,
                              'login.html',
                              {'form': form, 'password_is_wrong': True, 'error': 'Pls, Resubmit'})
        else:
            return render(request, 'login.html', {'form': form})

test:

def test_login_right(self, username='admin', password='zg123456'):
    """ POST right username or password """
    setup_test_environment()
    client = Client(enforce_csrf_checks=False)

    url = '/login/'
    response = self.client.post(url,
                                data={'username': username,
                                      'password': password},
                                secure=True,
                                follow=True)
    status_code = response.status_code
    self.assertNotIn(str(status_code)[0], ['4', '5'])
    self.assertIn('Welcome', response.content.decode('utf8'))

I find do test, auth.authenticate return None, but I use brower authenticate return not None, I don't know why, a protection mechanism？ I must use client.login func ?