Django - Unit test an object has been deleted - how to use assertRaise / DoesNotExist exception-CodePudding

I would lioke some help to unit test a function that deletes an object in a Django app

The problem
I display a list of values, it includes a bin icon to delete one value, and my view seems to work fine (at least according to the test I made).
How can I unit test it? I'm not able to find out the right way to do yet.
I searched the web and found the DoesNotExist exception, but I'm afraid I'm not able to use it, as I got a matching query does not exist error.
Could you please advise me on how to proceed?

What I tried
Here is my current whole code for the test:

class TestAdmUsers(TestCase):
    def setUp(self):
        self.company = create_dummy_company("Société de test")
        self.usr11 = create_dummy_user(self.company, "user11")
        self.usr13 = create_dummy_user(self.company, "user13")
        self.usr14 = create_dummy_user(self.company, "user14")
        self.client.force_login(self.user_staff.user)

    def test_delete_user(self):
        test_usercomp_id = self.usr13.id
        url = reverse("polls:adm_delete_user", args=[self.company.comp_slug, self.usr13.id])
        response = self.client.get(url, follow=True)
        self.assertRaises(UserComp.DoesNotExist, UserComp.objects.get(id=test_usercomp_id))

The test log is the following:

Creating test database for alias 'default'...
System check identified no issues (0 silenced).
E
======================================================================
ERROR: test_delete_user (polls.tests_admin.TestAdmUsers)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\Mes documents\Informatique\Developpement\Votes AG\projet_votes\polls\tests_admin.py", line 136, in test_delete_user
    self.assertRaises(UserComp.DoesNotExist, UserComp.objects.get(id=test_usercomp_id))
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\db\models\manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\db\models\query.py", line 408, in get
    self.model._meta.object_name
polls.models.UserComp.DoesNotExist: UserComp matching query does not exist.

----------------------------------------------------------------------
Ran 1 test in 1.763s

FAILED (errors=1)
Destroying test database for alias 'default'...

I made other tests like this one:

    def test_delete_user(self):
        url = reverse("polls:adm_delete_user", args=[self.company.comp_slug, self.usr13.id])
        response = self.client.get(url)
        self.assertContains(response, self.usr12.user.username)
        self.assertNotContains(response, self.usr13.user.username)

that leads to this:

======================================================================
FAIL: test_delete_user (polls.tests_admin.TestAdmUsers)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\Mes documents\Informatique\Developpement\Votes AG\projet_votes\polls\tests_admin.py", line 136, in test_delete_user
    self.assertNotContains(response, self.usr13.user.username)
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\test\testcases.py", line 465, in assertNotContains
    self.assertEqual(real_count, 0, msg_prefix   "Response should not contain %s" % text_repr)
AssertionError: 1 != 0 : Response should not contain 'user13'

----------------------------------------------------------------------

Or this one:

    def test_delete_user(self):
        test_usercomp_id = self.usr13.id
        url = reverse("polls:adm_delete_user", args=[self.company.comp_slug, self.usr13.id])
        response = self.client.get(url, follow=True)
        self.company.refresh_from_db()
        self.usr13.refresh_from_db()
        users = UserComp.get_users_in_comp(self.company.comp_slug)
        self.assertContains(response, self.usr12.user.username)
        self.assertNotContains(users, self.usr13)

with the following result:

======================================================================
ERROR: test_delete_user (polls.tests_admin.TestAdmUsers)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\Mes documents\Informatique\Developpement\Votes AG\projet_votes\polls\tests_admin.py", line 137, in test_delete_user
    self.usr13.refresh_from_db()
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\db\models\base.py", line 628, in refresh_from_db
    db_instance = db_instance_qs.get()
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\db\models\query.py", line 408, in get
    self.model._meta.object_name
polls.models.UserComp.DoesNotExist: UserComp matching query does not exist.

----------------------------------------------------------------------

And this latest one that uses a class method:

    def test_delete_user(self):
        current_username = self.usr13.user.username
        url = reverse("polls:adm_delete_user", args=[self.company.comp_slug, self.usr13.id])
        response = self.client.get(url, follow=True)
        self.company.refresh_from_db()
        self.usr13.refresh_from_db()
        self.assertContains(response, self.usr12.user.username)
        self.assertNotContains(UserComp.get_users_in_comp(self.company.comp_slug), self.usr13)

but the result is still an error:

`======================================================================
ERROR: test_delete_user (polls.tests_admin.TestAdmUsers)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\Mes documents\Informatique\Developpement\Votes AG\projet_votes\polls\tests_admin.py", line 137, in test_delete_user
    self.usr13.refresh_from_db()
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\db\models\base.py", line 628, in refresh_from_db
    db_instance = db_instance_qs.get()
  File "C:\Users\Christophe\.virtualenvs\projet_votes-onIieQ0I\lib\site-packages\django\db\models\query.py", line 408, in get
    self.model._meta.object_name
polls.models.UserComp.DoesNotExist: UserComp matching query does not exist.

----------------------------------------------------------------------

Related application code
Here is the code for the view:

def adm_delete_user(request, comp_slug, usr_id):
    del_usr = User.objects.get(pk=usr_id)
    msg = "Utilisateur {0} {1} supprimé.".format(del_usr.last_name, del_usr.first_name)
    User.objects.get(pk=usr_id).delete()

    messages.success(request, msg)
    return redirect("polls:adm_users", comp_slug=comp_slug)

And the model:

class UserComp(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE, verbose_name="Utilisateur")
    company = models.ForeignKey(Company, on_delete=models.CASCADE, verbose_name="Société")
    phone_regex = RegexValidator(regex=r'^0[0-9]([ .-]?[0-9]{2}){4}$', message=("Format de numéro de téléphone invalide"))
    phone_num = models.CharField("numéro de téléphone", validators=[phone_regex], max_length=14, null=True, blank=True)
    is_admin = models.BooleanField("administrateur", default=False)

    def __str__(self):
        return '%s %s' % (self.user.last_name, self.user.first_name)
    class Meta:
        verbose_name = "Liens Utilisateurs / Sociétés"
        verbose_name_plural = "Liens Utilisateurs / Sociétés"

    @classmethod
    def create_usercomp(cls, user, company, phone_num='', is_admin=False):
        """ Create a new UserComp """
        usr_comp = UserComp(user=user, company=company, phone_num=phone_num, is_admin=is_admin)
        usr_comp.save()
        return usr_comp

    @classmethod
    def get_users_in_comp(cls, comp_slug):
        user_list = cls.objects.filter(company__comp_slug=comp_slug)
        return user_list

Complementary search results
Finally, I found some posts here that oriented my tests, but I wasn't able to find the solution:

The most important to me leads me to assertRaise() test
Unfortunately, the one that asked how to use this exception has been closed, and referred to the previous one, but actually there is no information on how to proceed
This other one asking about the exception, and this one related to the error message did not give me any additional information.

CodePudding user response：

assertRaises takes a callable as its (optional) second argument. Since .get(...) is not a callable, you should use the context manager form instead:

with self.assertRaises(UserComp.DoesNotExist): 
    UserComp.objects.get(id=test_usercomp_id)