diff --git a/instances/tests/test_create_instance.py b/instances/tests/test_create_instance.py
index 5fb029aa..658bd54e 100644
--- a/instances/tests/test_create_instance.py
+++ b/instances/tests/test_create_instance.py
@@ -5,7 +5,7 @@ from unittest.mock import MagicMock, patch
 
 from computes.models import Compute
 from django.contrib.auth import get_user_model
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 from django.urls import reverse
 from instances.api.serializers import CreateInstanceSerializer
 from instances.models import Instance
@@ -164,7 +164,7 @@ class CreateInstanceViewTests(TestCase):
         conn.get_firmwares.assert_called_once_with("x86_64", "q35")
 
 
-class NicMacsTestCase(TestCase):
+class NicMacsTestCase(SimpleTestCase):
     def test_macs_follow_the_networks(self):
         self.assertEqual(nic_macs("52:54:00:00:00:01", "a,b"), ["52:54:00:00:00:01"])
         self.assertEqual(nic_macs("", "a,b"), [])
diff --git a/instances/tests/test_create_page_js.py b/instances/tests/test_create_page_js.py
index c5544207..d15280ba 100644
--- a/instances/tests/test_create_page_js.py
+++ b/instances/tests/test_create_page_js.py
@@ -9,7 +9,7 @@ import unittest
 from unittest.mock import patch
 
 from django.conf import settings
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 from django.urls import reverse
 from instances.forms import NewVMForm
 from instances.tests.create_page import render_create_page
@@ -183,7 +183,7 @@ console.log(JSON.stringify([field("#networks").value, field("#vm_mac").value]));
         self.assertEqual(NewVMForm.base_fields["mac"].clean(macs), macs)
 
 
-class DiskSourceAndPresetScriptTests(TestCase):
+class DiskSourceAndPresetScriptTests(SimpleTestCase):
     """The disk source choice enables only its own fields; a preset fills the
     sizes, picks a new disk and is announced."""
 
@@ -235,7 +235,7 @@ console.log(JSON.stringify({applied, cleared: pressed()}));""")
         self.assertEqual(out["cleared"], [["false", "text-body"], ["false", "text-body"]])
 
 
-class NewFormScriptTests(TestCase):
+class NewFormScriptTests(SimpleTestCase):
     """A new form starts with one interface; the template's copy goes into the
     template's pool unless the user picks another."""
 
diff --git a/instances/tests/test_xss.py b/instances/tests/test_xss.py
index a3061bb7..154f8594 100644
--- a/instances/tests/test_xss.py
+++ b/instances/tests/test_xss.py
@@ -8,7 +8,7 @@ from pathlib import Path
 from unittest.mock import patch
 
 from django.contrib.auth import get_user_model
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 from django.urls import reverse
 
 from accounts.models import UserInstance, UserSSHKey
@@ -99,7 +99,7 @@ class JsonEndpointContentTypeTestCase(TestCase):
         self.assertJson(self.client.get(reverse("vm_logs", args=[self.instance.pk])))
 
 
-class TemplateHtmlConcatenationTestCase(TestCase):
+class TemplateHtmlConcatenationTestCase(SimpleTestCase):
     """
     The log table and the volume dropdown are filled by JavaScript from JSON
     that contains user-entered names. They must use DOM APIs (.text()/.val())
@@ -142,7 +142,7 @@ ALLOWED_HTML_SINKS = {
 }
 
 
-class TemplateHtmlSinkInventoryTestCase(TestCase):
+class TemplateHtmlSinkInventoryTestCase(SimpleTestCase):
     def test_every_html_sink_in_templates_is_reviewed(self):
         found = set()
         for path in ROOT.glob("*/templates/**/*.html"):
diff --git a/operations/tests/test_kinds.py b/operations/tests/test_kinds.py
index 94655f1e..5ef8a25b 100644
--- a/operations/tests/test_kinds.py
+++ b/operations/tests/test_kinds.py
@@ -2,7 +2,7 @@ from datetime import timedelta
 from types import SimpleNamespace
 
 from django.contrib.auth import get_user_model
-from django.test import TestCase
+from django.test import SimpleTestCase, TestCase
 from django.utils import timezone
 
 from operations import jobs
@@ -11,7 +11,7 @@ from operations.models import TAKEOVER_AFTER, Claim, LeaseLost, Operation, Worke
 from operations.tests import fakes
 
 
-class RegistryTestCase(TestCase):
+class RegistryTestCase(SimpleTestCase):
     def test_kinds_register_by_name(self):
         self.assertIs(get_kind("test.noop"), KINDS["test.noop"])
         self.assertEqual((label_of("test.noop"), label_of("unknown.kind")), ("No-op", "unknown.kind"))
diff --git a/operations/tests/test_worker.py b/operations/tests/test_worker.py
index 5947d4e7..582ee827 100644
--- a/operations/tests/test_worker.py
+++ b/operations/tests/test_worker.py
@@ -12,7 +12,7 @@ from unittest.mock import patch
 from django.conf import settings
 from django.contrib.auth import get_user_model
 from django.db import OperationalError, connection
-from django.test import TransactionTestCase
+from django.test import SimpleTestCase, TransactionTestCase
 from django.utils import timezone
 
 from appsettings.models import AppSettings
@@ -345,14 +345,14 @@ class RequestJobTestCase(TransactionTestCase):
         self.assertEqual(fakes.EXPIRED, [str(other.pk)])
 
 
-class DataDirTestCase(TransactionTestCase):
+class DataDirTestCase(SimpleTestCase):
     def test_the_data_dir_does_not_follow_the_log_file(self):
         with self.settings(WEBVIRTCLOUD_LOG_FILE="/var/log/wvc-test/webvirtcloud.log"):
             moved = data_dir()
         self.assertEqual(str(moved), str(settings.BASE_DIR / "data"))
 
 
-class HostIdentityTestCase(TransactionTestCase):
+class HostIdentityTestCase(SimpleTestCase):
     def setUp(self):
         directory = tempfile.TemporaryDirectory()
         self.addCleanup(directory.cleanup)
diff --git a/webvirtcloud/tests/test_logging.py b/webvirtcloud/tests/test_logging.py
index 153560a8..f9a9a51e 100644
--- a/webvirtcloud/tests/test_logging.py
+++ b/webvirtcloud/tests/test_logging.py
@@ -4,17 +4,18 @@ path, not the process working directory."""
 import io
 import logging
 import os
+import shutil
 
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.http import HttpResponse
-from django.test import RequestFactory, TestCase
+from django.test import RequestFactory, SimpleTestCase, TestCase
 
 from webvirtcloud.log_context import RequestFilter
 from webvirtcloud.middleware import RequestIdMiddleware
 
 
-class LoggingConfigTestCase(TestCase):
+class LoggingConfigTestCase(SimpleTestCase):
     def test_default_handler_rotates(self):
         handler = settings.LOGGING["handlers"]["default"]
         self.assertEqual(handler["class"], "logging.handlers.RotatingFileHandler")
@@ -33,6 +34,7 @@ class LoggingConfigTestCase(TestCase):
         import tempfile
 
         tmp = tempfile.mkdtemp()
+        self.addCleanup(shutil.rmtree, tmp)
         log = os.path.join(tmp, "nested", "wvc.log")
         env = {
             **os.environ,