This is a much bigger issue.

Author: kingbuzzman

pytest_django/plugin.py

@@ -599,9 +599,10 @@ def _dj_autoclear_mailbox() -> None:
 
     from django.core import mail
 
-    del mail.outbox[:]
-    # if hasattr(main, "outbox"):
-    #     mail.outbox.clear()
+    # import ipdb; print('\a'); ipdb.sset_trace()
+    # del mail.outbox[:]
+    if hasattr(mail, "outbox"):
+        mail.outbox.clear()
 
 
 @pytest.fixture()

tests/test_environment.py

@@ -19,19 +19,39 @@
 
 
 @pytest.mark.django_project(
-    project_root="django_project_root",
     extra_settings="""
     EMAIL_BACKEND = "django.core.mail.backends.dummy.EmailBackend"
+    import unittest.mock
+    from types import SimpleNamespace
+
+    def setup_test_environment(*a, **k):
+        if hasattr(_TestState, "saved_data"):
+            # Executing this function twice would overwrite the saved values.
+            raise RuntimeError(
+                "setup_test_environment() was already called and can't be called "
+                "again without first calling teardown_test_environment()."
+            )
+
+        saved_data = SimpleNamespace()
+        _TestState.saved_data = saved_data
+        saved_data.allowed_hosts = []
+        saved_data.debug = False
+        saved_data.email_backend = None
+        saved_data.template_render = None
+
+    unittest.mock.patch("django.test.utils.setup_test_environment", setup_test_environment).start()
+    from django.test.utils import _TestState
     """,
 )
-def test_manage_test_runner(django_pytester: DjangoPytester) -> None:
+def test_mail_auto_fixture(django_pytester: DjangoPytester) -> None:
     django_pytester.create_test_module(
         """
         def test_bad_mail():
             pass
         """
     )
-    result = django_pytester.runpytest_subprocess("-s")
+    result = django_pytester.runpytest_subprocess("-s", "-vv")
+    print("\n".join([*result.outlines, *result.errlines]))
     assert "1 passed" in "\n".join([*result.outlines, *result.errlines])