Django CreateView test fail

Question

My configuration below (django 3.02):

Models:

class Assets(models.Model):
    assettag = models.CharField()
    ...

class Item(models.Model):
    asset = models.OneToOneField('Assets')
    ...

    def __str__(self):
        return (f"{self.rfid_tag}" + " - " + f"{self.asset.assettag}")

class Comments(models.Model): # I know, it should not be plural.
    item = models.ForeignKey('Item',
                             default=None,
                             null=True,
                             on_delete=models.CASCADE,
                             )
    text = models.TextField()
    ...

Form:

class ItemInsertForm(forms.ModelForm):
    rfid_tag = forms.CharField(label='RFID Tag',
                               widget=forms.TextInput(attrs={"placeholder":"96 bit EPC code",
                                                             "pattern":"^[a-fA-F0-9]{24}$",
                                                             "size":"25",
                                                             "id":"rfid_tag",
                                                             }
                                                      )
                               )
    asset = forms.CharField(label='AssetTag',
                            widget=forms.TextInput(attrs={"placeholder":"Item Inventory Tag",
                                                          "pattern":"{some regex}",
                                                          "size":"25",
                                                          "id":"asset",
                                                          }
                                                   )
                            )

    comments = forms.CharField(label='Comments',
                               required=False,
                               widget=forms.Textarea(attrs={"rows":5,
                                                            "cols":50,
                                                            "id":"comments",
                                                           }
                                                    )
                              )

    class Meta:
        model = Item
        fields = [
            'rfid_tag',
            'asset',
            'image',
            'date',
        ]


    def clean_rfid_tag(self, *args, **kwargs):
        return self.cleaned_data.get("rfid_tag").lower()

    def clean_asset(self, *args, **kwargs):
        AssetTag = self.cleaned_data.get("asset")
        try:
            _asset = Assets.objects.get(assettag = AssetTag)
        except Assets.DoesNotExist:
            raise forms.ValidationError("Asset does not exist !")
        self.Asset = _asset
        return self.Asset

View:

class InsertView(SuccessMessageMixin, AuditMixin, generic.CreateView):
    template_name = '{some template}'
    success_message = "Item succesfully created"
    form_class = ItemInsertForm

    def form_valid(self, form):
        item = form.save(commit=False)
        _comment = form.cleaned_data.get('comments')
        item = form.save()
        if _comment:
            item.comments_set.create(text =_comment)
        self.log_insert(item)
        return super().form_valid(form)

Test:

class TestViews(TestCase):
    @classmethod
    def setUpTestData(cls) -> None:
        # create dummy assets
        cls.asset = Assets.objects.create(assettag="{some assettag #1}",)
        cls.asset2 = Assets.objects.create(assettag="{some assettag #2}")
        # create dummy item
        cls.item = Item.objects.create(rfid_tag='abcdef012345678900000000', asset=cls.asset)

    def setUp(self) -> None:
        self.client = Client()
        self.insert_url = reverse('inventory:insert')

    def test_insert_POST_valid(self):
        response = self.client.post(self.insert_url,
                                    data = {'rfid_tag':'abcdef012345678900000001',
                                            'asset':'{some assettag #2}',}
                                    )
        new_item = Item.objects.get(rfid_tag="abcdef012345678900000001")
        self.assertEqual(response.status_code, 302)
        self.assertTrue(isinstance(new_item,Item))
        self.assertEqual(Item.objects.filter(rfid_tag="abcdef012345678900000001").count(),1)
        self.assertEqual(self.asset2.item, new_item)
        self.assertFalse(Comments.objects.all())

    def test_insert_POST_comment(self):
        response = self.client.post(self.insert_url,
                                    data = {'rfid_tag':'abcdef012345678900000001',
                                            'asset':'{some assettag #2}',
                                            'comments':'Test comment.',
                                            }
                                    )
        new_item = Item.objects.get(rfid_tag="abcdef012345678900000001")
        self.assertEqual(response.status_code, 302)
        self.assertTrue(isinstance(new_item,Item))
        self.assertEqual(Item.objects.filter(rfid_tag="abcdef012345678900000001").count(),1)
        self.assertEqual(self.asset2.item, new_item)
        self.assertTrue(isinstance(Comments.objects.get(text='Test comment.'), Comments))
        self.assertEqual(Comments.objects.get(text='Test comment.'),
                         new_item.comments_set.first())

If I run these tests, test_insert_POST_valid will fail due to assertion error:

AssertionError: < Item: abcdef012345678900000001 - {some assettag #2} > != < Item: abcdef012345678900000001 - {some assettag #2} >

I have inserted some print statements throughout the code:

    # this was placed first in both tests, before the POST request
    items = Item.objects.all()
    for item in items:
        print("Item:",item.id, " - ", item)

    # and then again, after each POST request

What I noticed is that the first time the prints run, it will output just one Item object (this is true for both functions):

Item: 1 - abcdef012345678900000009 - {some assettag #1}

but on the second run (after the POST request is sent and the new item is created):

For test_insert_POST_comment the result is:

Item: 1 - abcdef012345678900000009 - {some assettag #1}
Item: 2 - abcdef012345678900000001 - {some assettag #2}

While for test_insert_POST_valid the result is:

Item: 1 - abcdef012345678900000009 - {some assettag #1}
Item: 3 - abcdef012345678900000001 - {some assettag #2}

If I do print("Asset Item:", self.asset2.item.id, " - ", self.asset2.item) in the test_insert_POST_valid function (for some reason this test runs second) it will output:

Asset Item: 2 - abcdef012345678900000001 - {some assettag #2}

I don't understand how this happens. Item.objects.all() will only return one object (abcdef012345678900000000), while the Asset object still maintains a relationship with a fictive second Item object, that does not exist.

I was suspecting that test_insert_POST_valid is not actually creating any object, since self.asset2 already has an Item associated throug a OneToOne relationship, but this is not true. If I change the rfid_tag value to abcdef012345678900000002 (or whatever), it will create the new Item, but self.asset2.item will still point to abcdef012345678900000001.

What is the cause of this issue and wow can I solve it? (Putting self.asset2.item = None before POST-ing the data, will not help. A new relationship will not be created.)

Edit: I could move cls.asset2 = Assets.objects.create(assettag="{some assettag #2}") in the setUp method and it will be created before each test, but I have some more logic depending on this I would have to move it too. The prefered way is to leave it in setUpTestdata so it runs only once.

Answer 1

I have found a simple solution: Add self.asset2.refresh_from_db() in the setUp method. This will reload every field of this model from the database, before every test is ran.