Django test.py model object instance is limited to one test

Question

Okay this is pretty strange. This is my code that works:

test.py

from django.test import TestCase
from django.urls import reverse, resolve
from django.utils import timezone
import datetime

from ..models import Realtor, Listing, Contact
from ..views import listing

from django.test import override_settings
from PIL import Image
from io import BytesIO
from django.core.files import File
import tempfile

def get_image_file(name='test.png', ext='png', size=(50, 50), color=(256, 0, 0)):
    file_obj = BytesIO()
    image = Image.new("RGB", size=size, color=color)
    image.save(file_obj, ext)
    file_obj.seek(0)
    return File(file_obj, name=name)

class RealestateListingViewTest(TestCase):
    @override_settings(MEDIA_ROOT=tempfile.TemporaryDirectory(prefix='mediatest').name)
    def setUp(self):
        image_file = get_image_file
        Realtor.objects.create(name='sample_realtor', photo=get_image_file())
        Listing.objects.create(title='listing_sample', address='sample', realtor=Realtor.objects.get(pk=1), city='sample', state='sample', zipcode='1234', price='555555', bedrooms='1', bathrooms='1', garage='1', sqft='123', lot_size='123', photo_main=get_image_file(), photo_1=get_image_file(), photo_2=get_image_file(), photo_3=get_image_file(), photo_4=get_image_file(), photo_5=get_image_file(), photo_6=get_image_file())
        url = reverse('btre:listing', kwargs={'listing_id': 1})
        self.response = self.client.get(url)

    def test_listing_status_code(self):
        self.assertEquals(self.response.status_code, 200)

The above code works but whenever I add another test to the mix, like:

    def test_listing_url_resolves_listing_view(self):
        view = resolve('/realestate/listing/1')
        self.assertEqual(view.func, listing)

I get this error:

======================================================================
ERROR: test_listing_url_resolves_listing_view (realestate.tests.test_view_listing.RealestateListingViewTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\Storm\Dev\btre_project\realestate\tests\test_view_listing.py", line 35, in setUp
    Listing.objects.create(title='listing_sample', address='sample', realtor=Realtor.objects.get(pk=1), city='sample', state='sample', zipcode='1234', price='555555', bedrooms='1', bathrooms='1', garage='1', sqft='123', lot_size='123', photo_main=get_image_file(), photo_1=get_image_file(), photo_2=get_image_file(), photo_3=get_image_file(), photo_4=get_image_file(), photo_5=get_image_file(), photo_6=get_image_file())
  File "C:\Users\Storm\Envs\btre\lib\site-packages\django\db\models\manager.py", line 82, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\Storm\Envs\btre\lib\site-packages\django\db\models\query.py", line 408, in get
    self.model._meta.object_name
realestate.models.Realtor.DoesNotExist: Realtor matching query does not exist.

Anyone have an idea how or why this is happening?

Also note that it works as long as there is only one test existing in the TestCase class which is why it is very strange to me.

Also I have tried this method for the image file creation:

class RealestateListingViewTest(TestCase):
    @staticmethod
    def get_image_file(name='test.png', ext='png', size=(50, 50), color=(256, 0, 0)):
        file_obj = BytesIO()
        image = Image.new("RGB", size=size, color=color)
        image.save(file_obj, ext)
        file_obj.seek(0)
        return File(file_obj, name=name)

Answer 1

You haven't shown the view that you're testing, but presumably the 1 in that URL is the PK of the object.

The issue is that although the database is cleared after every test, sequences are not reset. So the second time you create an item in the setUp method, its PK will not be 1.

You shouldn't rely on specific IDs. Assign the created item to a variable and use it:

    listing = Listing.objects.create(title='listing_sample', address='sample', realtor=Realtor.objects.get(pk=1), city='sample', state='sample', zipcode='1234', price='555555', bedrooms='1', bathrooms='1', garage='1', sqft='123', lot_size='123', photo_main=get_image_file(), photo_1=get_image_file(), photo_2=get_image_file(), photo_3=get_image_file(), photo_4=get_image_file(), photo_5=get_image_file(), photo_6=get_image_file())
    url = reverse('btre:listing', kwargs={'listing_id': listing.id})