class UserDetail(RetrieveModelMixin, DestroyModelMixin, UpdateModelMixin, GenericViewSet):
    authentication_classes = (BasicAuthentication, TokenAuthentication)
    permission_classes = IsAuthenticated,
    queryset = CustomUser.objects.all()
    serializer_class = UserSerializer

class AccountTests(APITestCase):

    def setUp(self):
        self.user = CustomUser.objects.create_user(email="user1@test.com", password="password1", is_staff=True)
        self.user.save()
        self.user = CustomUser.objects.get(email="user1@test.com")
        self.client = APIClient()

    def test_add_name(self):
        self.client.login(email="user1@test.com", password='password1')
        url = reverse('customuser-detail', args=(self.user.id,))
        data = {'first_name': 'test', 'last_name': 'user'}

        self.client.login(email="user1@test.com", password='password1')
        response = self.client.put(url, data, format='json')

        self.assertEqual(response.status_code, status.HTTP_200_OK)

{u'detail': u'Authentication credentials were not provided.'}

self.user = CustomUser.objects.create_user(email="user1@test.com", is_staff=True)
self.user.set_password("password1")
self.user.save()

self.client.force_login(
    user=User.objects.first(),
    backend='django.contrib.auth.backends.ModelBackend' # one of your AUTHENTICATION_BACKENDS
)