fix: prevent Django tests from destroying production D1/DO data

django_cf/db/base_engine.py

@@ -1,5 +1,6 @@
 import re
 import sqlparse
+from django.core.exceptions import ImproperlyConfigured
 from django.db import DatabaseError, Error, DataError, OperationalError, \
     IntegrityError, InternalError, ProgrammingError, NotSupportedError, InterfaceError
 from django.db.backends.sqlite3.base import DatabaseWrapper as SQLiteDatabaseWrapper
@@ -58,7 +59,37 @@ class CFDatabaseIntrospection(SQLiteDatabaseIntrospection):
 
 
 class CFDatabaseCreation(SQLiteDatabaseCreation):
-    pass
+    def _create_test_db(self, verbosity, autoclobber, keepdb=False):
+        """
+        Prevent accidental test runs against production Cloudflare databases.
+
+        Cloudflare D1 and Durable Objects do not support isolated test databases
+        or transactions. Running Django tests directly against these backends will
+        DESTROY all production data because the backend connects via
+        CLOUDFLARE_DATABASE_ID (or binding), not via the NAME setting, so the
+        test runner ends up migrating and flushing the production database.
+        """
+        raise ImproperlyConfigured(
+            "\n"
+            "Running Django tests against Cloudflare D1/Durable Objects is not "
+            "supported because these backends do not support isolated test "
+            "databases or transactions.\n\n"
+            "Testing against these backends will DESTROY your production data.\n\n"
+            "To run tests safely, create a separate Django settings module for "
+            "testing and switch to a different database engine there. Example:\n\n"
+            "    # settings/test.py\n"
+            "    from .settings import *\n\n"
+            "    DATABASES = {\n"
+            "        'default': {\n"
+            "            'ENGINE': 'django.db.backends.sqlite3',\n"
+            "            'NAME': BASE_DIR / 'test_db.sqlite3',\n"
+            "        }\n"
+            "    }\n\n"
+            "Then run tests with:\n"
+            "    python manage.py test --settings=settings.test\n\n"
+            "Or point CLOUDFLARE_DATABASE_ID to a dedicated test D1 database in "
+            "your test settings module.\n"
+        )
 
 
 class CFDatabaseClient(SQLiteDatabaseClient):

tests/db/test_creation_safety.py

@@ -0,0 +1,53 @@
+"""Tests for CFDatabaseCreation test database safety guard."""
+import pytest
+from unittest.mock import MagicMock
+from django.core.exceptions import ImproperlyConfigured
+
+from django_cf.db.base_engine import CFDatabaseCreation
+
+
+class TestCFDatabaseCreationTestSafety:
+    """Tests for CFDatabaseCreation _create_test_db safety guard."""
+
+    def _get_creation(self, test_settings=None):
+        """Create a CFDatabaseCreation instance with mocked connection."""
+        mock_connection = MagicMock()
+        mock_connection.settings_dict = {"TEST": test_settings or {}}
+        return CFDatabaseCreation(mock_connection)
+
+    def test_create_test_db_always_raises_error(self):
+        """Test that _create_test_db ALWAYS raises ImproperlyConfigured."""
+        creation = self._get_creation(test_settings={})
+
+        with pytest.raises(ImproperlyConfigured) as exc_info:
+            creation._create_test_db(verbosity=0, autoclobber=False)
+
+        error_msg = str(exc_info.value)
+        assert "Running Django tests against Cloudflare D1/Durable Objects is not supported" in error_msg
+        assert "DESTROY your production data" in error_msg
+        assert "settings/test.py" in error_msg
+        assert "django.db.backends.sqlite3" in error_msg
+
+    def test_create_test_db_raises_even_when_test_name_is_set(self):
+        """Test that _create_test_db still raises when TEST['NAME'] is configured."""
+        # Setting TEST['NAME'] does NOT isolate D1 databases because the D1
+        # backend connects via CLOUDFLARE_DATABASE_ID, not NAME.
+        creation = self._get_creation(test_settings={"NAME": ":memory:"})
+
+        with pytest.raises(ImproperlyConfigured) as exc_info:
+            creation._create_test_db(verbosity=0, autoclobber=False)
+
+        error_msg = str(exc_info.value)
+        assert "DESTROY your production data" in error_msg
+
+    def test_error_message_includes_safe_config_example(self):
+        """Test that error message includes example safe configuration."""
+        creation = self._get_creation(test_settings={})
+
+        with pytest.raises(ImproperlyConfigured) as exc_info:
+            creation._create_test_db(verbosity=0, autoclobber=False)
+
+        error_msg = str(exc_info.value)
+        assert "settings/test.py" in error_msg
+        assert "--settings=settings.test" in error_msg
+        assert "django.db.backends.sqlite3" in error_msg