Reset sequences in a project-wide fixture and revert most changes

Author: browniebroke

tests/conftest.py

@@ -3,7 +3,36 @@
 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
+from django.test import TestCase, TransactionTestCase
+
+
+@pytest.fixture(autouse=True)
+def _reset_sequences(request):
+    """Reset all database sequences so PKs start from 1 in each test.
+
+    PostgreSQL sequences are non-transactional and persist across
+    TestCase's transaction rollbacks. This fixture ensures every test
+    gets predictable PKs starting from 1 regardless of execution order.
+    No-op on SQLite and skipped for tests that don't use the database.
+    """
+    if connection.vendor != 'postgresql':
+        return
+    # Only run for tests that actually have database access.
+    if not (request.cls and issubclass(request.cls, (TestCase, TransactionTestCase))):
+        if 'db' not in request.fixturenames and 'transactional_db' not in request.fixturenames:
+            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

@@ -119,8 +119,9 @@ def test_post_root_view(self):
         with self.assertNumQueries(1):
             response = self.view(request).render()
         assert response.status_code == status.HTTP_201_CREATED
-        created = self.objects.get(text='foobar')
-        assert response.data == {'id': created.pk, 'text': 'foobar'}
+        assert response.data == {'id': 4, 'text': 'foobar'}
+        created = self.objects.get(id=4)
+        assert created.text == 'foobar'
 
     def test_put_root_view(self):
         """
@@ -152,8 +153,9 @@ def test_post_cannot_set_id(self):
         with self.assertNumQueries(1):
             response = self.view(request).render()
         assert response.status_code == status.HTTP_201_CREATED
-        created = self.objects.get(text='foobar')
-        assert response.data == {'id': created.pk, 'text': 'foobar'}
+        assert response.data == {'id': 4, 'text': 'foobar'}
+        created = self.objects.get(id=4)
+        assert created.text == 'foobar'
 
     def test_post_error_root_view(self):
         """
@@ -175,11 +177,8 @@ def setUp(self):
         Create 3 BasicModel instances.
         """
         items = ['foo', 'bar', 'baz', 'filtered out']
-        self.created_items = []
         for item in items:
-            obj = BasicModel.objects.create(text=item)
-            if item != 'filtered out':
-                self.created_items.append(obj)
+            BasicModel(text=item).save()
         self.objects = BasicModel.objects.exclude(text='filtered out')
         self.data = [
             {'id': obj.id, 'text': obj.text}
@@ -192,10 +191,9 @@ def test_get_instance_view(self):
         """
         GET requests to RetrieveUpdateDestroyAPIView should return a single object.
         """
-        pk = self.created_items[0].pk
-        request = factory.get(f'/{pk}')
+        request = factory.get('/1')
         with self.assertNumQueries(1):
-            response = self.view(request, pk=pk).render()
+            response = self.view(request, pk=1).render()
         assert response.status_code == status.HTTP_200_OK
         assert response.data == self.data[0]
 
@@ -214,43 +212,40 @@ def test_put_instance_view(self):
         """
         PUT requests to RetrieveUpdateDestroyAPIView should update an object.
         """
-        pk = self.created_items[0].pk
         data = {'text': 'foobar'}
-        request = factory.put(f'/{pk}', data, format='json')
+        request = factory.put('/1', data, format='json')
         with self.assertNumQueries(EXPECTED_QUERIES_FOR_PUT):
-            response = self.view(request, pk=str(pk)).render()
+            response = self.view(request, pk='1').render()
         assert response.status_code == status.HTTP_200_OK
-        assert dict(response.data) == {'id': pk, 'text': 'foobar'}
-        updated = self.objects.get(id=pk)
+        assert dict(response.data) == {'id': 1, 'text': 'foobar'}
+        updated = self.objects.get(id=1)
         assert updated.text == 'foobar'
 
     def test_patch_instance_view(self):
         """
         PATCH requests to RetrieveUpdateDestroyAPIView should update an object.
         """
-        pk = self.created_items[0].pk
         data = {'text': 'foobar'}
-        request = factory.patch(f'/{pk}', data, format='json')
+        request = factory.patch('/1', data, format='json')
 
         with self.assertNumQueries(EXPECTED_QUERIES_FOR_PUT):
-            response = self.view(request, pk=pk).render()
+            response = self.view(request, pk=1).render()
         assert response.status_code == status.HTTP_200_OK
-        assert response.data == {'id': pk, 'text': 'foobar'}
-        updated = self.objects.get(id=pk)
+        assert response.data == {'id': 1, 'text': 'foobar'}
+        updated = self.objects.get(id=1)
         assert updated.text == 'foobar'
 
     def test_delete_instance_view(self):
         """
         DELETE requests to RetrieveUpdateDestroyAPIView should delete an object.
         """
-        pk = self.created_items[0].pk
-        request = factory.delete(f'/{pk}')
+        request = factory.delete('/1')
         with self.assertNumQueries(2):
-            response = self.view(request, pk=pk).render()
+            response = self.view(request, pk=1).render()
         assert response.status_code == status.HTTP_204_NO_CONTENT
         assert response.content == b''
         ids = [obj.id for obj in self.objects.all()]
-        assert ids == [self.created_items[1].pk, self.created_items[2].pk]
+        assert ids == [2, 3]
 
     def test_get_instance_view_incorrect_arg(self):
         """
@@ -266,27 +261,25 @@ def test_put_cannot_set_id(self):
         """
         PUT requests to create a new object should not be able to set the id.
         """
-        pk = self.created_items[0].pk
         data = {'id': 999, 'text': 'foobar'}
-        request = factory.put(f'/{pk}', data, format='json')
+        request = factory.put('/1', data, format='json')
         with self.assertNumQueries(EXPECTED_QUERIES_FOR_PUT):
-            response = self.view(request, pk=pk).render()
+            response = self.view(request, pk=1).render()
         assert response.status_code == status.HTTP_200_OK
-        assert response.data == {'id': pk, 'text': 'foobar'}
-        updated = self.objects.get(id=pk)
+        assert response.data == {'id': 1, 'text': 'foobar'}
+        updated = self.objects.get(id=1)
         assert updated.text == 'foobar'
 
     def test_put_to_deleted_instance(self):
         """
         PUT requests to RetrieveUpdateDestroyAPIView should return 404 if
         an object does not currently exist.
         """
-        pk = self.created_items[0].pk
-        self.objects.get(id=pk).delete()
+        self.objects.get(id=1).delete()
         data = {'text': 'foobar'}
-        request = factory.put(f'/{pk}', data, format='json')
+        request = factory.put('/1', data, format='json')
         with self.assertNumQueries(1):
-            response = self.view(request, pk=pk).render()
+            response = self.view(request, pk=1).render()
         assert response.status_code == status.HTTP_404_NOT_FOUND
 
     def test_put_to_filtered_out_instance(self):
@@ -305,21 +298,19 @@ def test_patch_cannot_create_an_object(self):
         PATCH requests should not be able to create objects.
         """
         data = {'text': 'foobar'}
-        non_existent_pk = 999999
-        request = factory.patch(f'/{non_existent_pk}', data, format='json')
+        request = factory.patch('/999', data, format='json')
         with self.assertNumQueries(1):
-            response = self.view(request, pk=non_existent_pk).render()
+            response = self.view(request, pk=999).render()
         assert response.status_code == status.HTTP_404_NOT_FOUND
-        assert not self.objects.filter(id=non_existent_pk).exists()
+        assert not self.objects.filter(id=999).exists()
 
     def test_put_error_instance_view(self):
         """
         Incorrect PUT requests in HTML should include a form error.
         """
-        pk = self.created_items[0].pk
         data = {'text': 'foobar' * 100}
         request = factory.put('/', data, HTTP_ACCEPT='text/html')
-        response = self.view(request, pk=pk).render()
+        response = self.view(request, pk=1).render()
         expected_error = '<span class="help-block">Ensure this field has no more than 100 characters.</span>'
         assert expected_error in response.rendered_content.decode()
 
@@ -354,10 +345,8 @@ def setUp(self):
         Create 3 BasicModel instances.
         """
         items = ['foo', 'bar', 'baz']
-        self.created_items = []
         for item in items:
-            obj = BasicModel.objects.create(text=item)
-            self.created_items.append(obj)
+            BasicModel(text=item).save()
         self.objects = BasicModel.objects
         self.data = [
             {'id': obj.id, 'text': obj.text}
@@ -380,10 +369,9 @@ def test_overridden_get_object_view(self):
         """
         GET requests to RetrieveUpdateDestroyAPIView should return a single object.
         """
-        pk = self.created_items[0].pk
-        request = factory.get(f'/{pk}')
+        request = factory.get('/1')
         with self.assertNumQueries(1):
-            response = self.view(request, pk=pk).render()
+            response = self.view(request, pk=1).render()
         assert response.status_code == status.HTTP_200_OK
         assert response.data == self.data[0]
 
@@ -416,7 +404,7 @@ def test_create_model_with_auto_now_add_field(self):
         request = factory.post('/', data, format='json')
         response = self.view(request).render()
         assert response.status_code == status.HTTP_201_CREATED
-        created = self.objects.get(content='foobar')
+        created = self.objects.get(id=1)
         assert created.content == 'foobar'
 
 
@@ -495,10 +483,8 @@ def setUp(self):
         Create 3 BasicModel instances to filter on.
         """
         items = ['foo', 'bar', 'baz']
-        self.created_items = []
         for item in items:
-            obj = BasicModel.objects.create(text=item)
-            self.created_items.append(obj)
+            BasicModel(text=item).save()
         self.objects = BasicModel.objects
         self.data = [
             {'id': obj.id, 'text': obj.text}
@@ -514,8 +500,7 @@ def test_get_root_view_filters_by_name_with_filter_backend(self):
         response = root_view(request).render()
         assert response.status_code == status.HTTP_200_OK
         assert len(response.data) == 1
-        foo_obj = self.created_items[0]
-        assert response.data == [{'id': foo_obj.pk, 'text': 'foo'}]
+        assert response.data == [{'id': 1, 'text': 'foo'}]
 
     def test_get_root_view_filters_out_all_models_with_exclusive_filter_backend(self):
         """
@@ -531,10 +516,9 @@ def test_get_instance_view_filters_out_name_with_filter_backend(self):
         """
         GET requests to RetrieveUpdateDestroyAPIView should raise 404 when model filtered out.
         """
-        pk = self.created_items[0].pk
         instance_view = InstanceView.as_view(filter_backends=(ExclusiveFilterBackend,))
-        request = factory.get(f'/{pk}')
-        response = instance_view(request, pk=pk).render()
+        request = factory.get('/1')
+        response = instance_view(request, pk=1).render()
         assert response.status_code == status.HTTP_404_NOT_FOUND
         assert response.data == {
             'detail': ErrorDetail(
@@ -547,12 +531,11 @@ def test_get_instance_view_will_return_single_object_when_filter_does_not_exclud
         """
         GET requests to RetrieveUpdateDestroyAPIView should return a single object when not excluded
         """
-        foo_obj = self.created_items[0]
         instance_view = InstanceView.as_view(filter_backends=(InclusiveFilterBackend,))
-        request = factory.get(f'/{foo_obj.pk}')
-        response = instance_view(request, pk=foo_obj.pk).render()
+        request = factory.get('/1')
+        response = instance_view(request, pk=1).render()
         assert response.status_code == status.HTTP_200_OK
-        assert response.data == {'id': foo_obj.pk, 'text': 'foo'}
+        assert response.data == {'id': 1, 'text': 'foo'}
 
     def test_dynamic_serializer_form_in_browsable_api(self):
         """

tests/test_generics.py

@@ -760,7 +760,7 @@ class DisplayValueModel(models.Model):
 
 class TestRelationalFieldDisplayValue(TestCase):
     def setUp(self):
-        self.targets = DisplayValueTargetModel.objects.bulk_create([
+        DisplayValueTargetModel.objects.bulk_create([
             DisplayValueTargetModel(name='Red'),
             DisplayValueTargetModel(name='Yellow'),
             DisplayValueTargetModel(name='Green'),
@@ -773,7 +773,7 @@ class Meta:
                 fields = '__all__'
 
         serializer = TestSerializer()
-        expected = {t.pk: '%s Color' % t.name for t in self.targets}
+        expected = {1: 'Red Color', 2: 'Yellow Color', 3: 'Green Color'}
         self.assertEqual(serializer.fields['color'].choices, expected)
 
     def test_custom_display_value(self):
@@ -789,7 +789,7 @@ class Meta:
                 fields = '__all__'
 
         serializer = TestSerializer()
-        expected = {t.pk: 'My %s Color' % t.name for t in self.targets}
+        expected = {1: 'My Red Color', 2: 'My Yellow Color', 3: 'My Green Color'}
         self.assertEqual(serializer.fields['color'].choices, expected)
 
 
@@ -1278,10 +1278,10 @@ class Meta:
         parent_serializer = TestParentModelSerializer(parent)
         child_serializer = TestChildModelSerializer(child)
 
-        parent_expected = {'children': ['def'], 'id': parent.pk, 'title': 'abc'}
+        parent_expected = {'children': ['def'], 'id': 1, 'title': 'abc'}
         self.assertEqual(parent_serializer.data, parent_expected)
 
-        child_expected = {'parent': parent.pk, 'value': 'def'}
+        child_expected = {'parent': 1, 'value': 'def'}
         self.assertEqual(child_serializer.data, child_expected)