Fix CI test to actually use the Postgres database

pyproject.toml

@@ -115,7 +115,7 @@ max_supported_python = "3.14"
 keep_full_version = true
 
 [tool.pytest.ini_options]
-addopts = "--tb=short --strict-markers -ra"
+addopts = "--tb=short --strict-markers -ra --no-migrations"
 testpaths = [ "tests" ]
 markers = [
   "requires_postgres: marks tests as requiring a PostgreSQL database backend",

rest_framework/test.py

@@ -1,11 +1,14 @@
 # Note that we import as `DjangoRequestFactory` and `DjangoClient` in order
 # to make it harder for the user to import the wrong thing without realizing.
 import io
+from contextlib import contextmanager
 from importlib import import_module
 
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.core.handlers.wsgi import WSGIHandler
+from django.core.signals import request_finished, request_started
+from django.db import close_old_connections
 from django.test import override_settings, testcases
 from django.test.client import Client as DjangoClient
 from django.test.client import ClientHandler
@@ -22,6 +25,21 @@ def force_authenticate(request, user=None, token=None):
     request._force_auth_token = token
 
 
+@contextmanager
+def _keep_connections_open():
+    """
+    Prevent Django from closing the database connection while a request
+    is dispatched, matching the behavior of Django's ClientHandler.
+    """
+    request_started.disconnect(close_old_connections)
+    request_finished.disconnect(close_old_connections)
+    try:
+        yield
+    finally:
+        request_started.connect(close_old_connections)
+        request_finished.connect(close_old_connections)
+
+
 if requests is not None:
     class HeaderDict(requests.packages.urllib3._collections.HTTPHeaderDict):
         def get_all(self, key, default):
@@ -90,7 +108,8 @@ def start_response(wsgi_status, wsgi_headers, exc_info=None):
 
             # Make the outgoing request via WSGI.
             environ = self.get_environ(request)
-            wsgi_response = self.app(environ, start_response)
+            with _keep_connections_open():
+                wsgi_response = self.app(environ, start_response)
 
             # Build the underlying urllib3.HTTPResponse
             raw_kwargs['body'] = io.BytesIO(b''.join(wsgi_response))

tests/conftest.py

@@ -3,7 +3,31 @@
 import dj_database_url
 import django
 import pytest
+from django.apps import apps
 from django.core import management
+from django.core.management.color import no_style
+from django.db import connection
+
+
+@pytest.fixture
+def reset_sequences():
+    """
+    Reset all database sequences so PKs start from 1.
+
+    PostgreSQL sequences are non-transactional and persist across
+    TestCase's transaction rollbacks. Apply this fixture to test
+    classes that rely on hardcoded PKs to keep them predictable
+    regardless of execution order. No-op on SQLite.
+    """
+    if connection.vendor != 'postgresql':
+        return
+    table_names = set(connection.introspection.table_names())
+    models = [m for m in apps.get_models() if m._meta.db_table in table_names]
+    sql_list = connection.ops.sequence_reset_sql(no_style(), models)
+    if sql_list:
+        with connection.cursor() as cursor:
+            for sql in sql_list:
+                cursor.execute(sql)
 
 
 def pytest_addoption(parser):

tests/test_filters.py

@@ -45,7 +45,7 @@ def test_filter_queryset_raises_error(self):
 
 
 class SearchFilterModel(models.Model):
-    title = models.CharField(max_length=20)
+    title = models.CharField(max_length=25)
     text = models.CharField(max_length=100)
 
 
@@ -459,6 +459,7 @@ class Meta:
         fields = '__all__'
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class SearchFilterM2MTests(TestCase):
     def setUp(self):
         # Sequence of title/text/attributes is:
@@ -657,6 +658,7 @@ class Meta:
         fields = '__all__'
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class OrderingFilterTests(TestCase):
     def setUp(self):
         # Sequence of title/text is:
@@ -974,6 +976,7 @@ class Meta:
         fields = ('id', 'user')
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class SensitiveOrderingFilterTests(TestCase):
     def setUp(self):
         for idx in range(3):

tests/test_generics.py

@@ -76,6 +76,7 @@ class SlugBasedInstanceView(InstanceView):
 
 
 # Tests
+@pytest.mark.usefixtures("reset_sequences")
 class TestRootView(TestCase):
     def setUp(self):
         """
@@ -171,6 +172,7 @@ def test_post_error_root_view(self):
 EXPECTED_QUERIES_FOR_PUT = 2
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class TestInstanceView(TestCase):
     def setUp(self):
         """
@@ -334,6 +336,7 @@ def setUp(self):
         self.view = FKInstanceView.as_view()
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class TestOverriddenGetObject(TestCase):
     """
     Test cases for a RetrieveUpdateDestroyAPIView that does NOT use the
@@ -477,6 +480,7 @@ class Meta:
         return DynamicSerializer
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class TestFilterBackendAppliedToViews(TestCase):
     def setUp(self):
         """

tests/test_model_serializer.py

@@ -758,6 +758,7 @@ class DisplayValueModel(models.Model):
     color = models.ForeignKey(DisplayValueTargetModel, on_delete=models.CASCADE)
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class TestRelationalFieldDisplayValue(TestCase):
     def setUp(self):
         DisplayValueTargetModel.objects.bulk_create([

tests/test_pagination.py

@@ -1045,6 +1045,7 @@ class CursorPaginationModel(models.Model):
     created = models.IntegerField()
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class TestCursorPaginationWithValueQueryset(CursorPaginationTestsMixin, TestCase):
     """
     Unit tests for `pagination.CursorPagination` for value querysets.

tests/test_permissions.py

@@ -2,6 +2,7 @@
 import unittest
 from unittest import mock
 
+import pytest
 from django.conf import settings
 from django.contrib.auth.models import AnonymousUser, Group, Permission, User
 from django.db import models
@@ -73,6 +74,7 @@ def basic_auth_header(username, password):
     return 'Basic %s' % base64_credentials
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class ModelPermissionsIntegrationTests(TestCase):
     def setUp(self):
         User.objects.create_user('disallowed', 'disallowed@example.com', 'password')
@@ -325,6 +327,7 @@ def get_queryset(self):
 get_queryset_object_permissions_view = GetQuerysetObjectPermissionInstanceView.as_view()
 
 
+@pytest.mark.usefixtures("reset_sequences")
 @unittest.skipUnless('guardian' in settings.INSTALLED_APPS, 'django-guardian not installed')
 class ObjectPermissionsIntegrationTests(TestCase):
     """
@@ -504,6 +507,7 @@ class DeniedObjectViewWithDetail(PermissionInstanceView):
 denied_object_view_with_detail = DeniedObjectViewWithDetail.as_view()
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class CustomPermissionsTests(TestCase):
     def setUp(self):
         BasicModel(text='foo').save()

tests/test_prefetch_related.py

@@ -1,3 +1,4 @@
+import pytest
 from django.contrib.auth.models import Group, User
 from django.test import TestCase
 
@@ -18,6 +19,7 @@ class UserUpdate(generics.UpdateAPIView):
     serializer_class = UserSerializer
 
 
+@pytest.mark.usefixtures("reset_sequences")
 class TestPrefetchRelatedUpdates(TestCase):
     def setUp(self):
         self.user = User.objects.create(username='tom', email='tom@example.com')