diff --git a/trovi/models.py b/trovi/models.py
index c997e6f..59736c0 100644
--- a/trovi/models.py
+++ b/trovi/models.py
@@ -300,7 +300,7 @@ def generate_slug(instance: "ArtifactVersion", created: bool = False, **_):
             with transaction.atomic():
                 if instance.artifact:
                     versions_today_query = instance.artifact.versions.filter(
-                        artifact__created_at__date=instance.created_at.date(),
+                        created_at__date=instance.created_at.date(),
                     ).select_for_update()
                     versions_today = versions_today_query.exclude(
                         slug__exact=""
diff --git a/trovi/settings.py b/trovi/settings.py
index 63a0628..f08050f 100644
--- a/trovi/settings.py
+++ b/trovi/settings.py
@@ -14,6 +14,7 @@
 from pathlib import Path
 
 # Build paths inside the project like this: BASE_DIR / 'subdir'.
+import sys
 from urllib.parse import urlparse
 
 BASE_DIR = Path(__file__).resolve().parent.parent
@@ -124,7 +125,7 @@
     # Plugins
     "rest_framework",
     "drf_spectacular",
-    'corsheaders',
+    "corsheaders",
     # Trovi
     "trovi.apps.TroviConfig",
     "trovi.api.apps.ApiConfig",
@@ -191,8 +192,9 @@
 
 # Database
 # https://docs.djangoproject.com/en/3.2/ref/settings/#databases
+TESTING = "test" in sys.argv or "test_coverage" in sys.argv
 
-if os.getenv("DB_ENGINE"):
+if not TESTING and os.getenv("DB_ENGINE"):
     DATABASES = {
         "default": {
             "ENGINE": os.getenv("DB_ENGINE"),
diff --git a/util/sql_format.py b/util/sql_format.py
index 3ddcaf5..b7826ae 100644
--- a/util/sql_format.py
+++ b/util/sql_format.py
@@ -1,4 +1,5 @@
 """Pretty-Print SQL queries for console output."""
+
 from logging import Formatter
 
 from django.conf import settings
diff --git a/util/test.py b/util/test.py
index 56e54c7..e775f35 100644
--- a/util/test.py
+++ b/util/test.py
@@ -3,6 +3,7 @@
 Not meant to be robust, and mostly unvalidated, but helpful to avoid
 having to reference dicts with strings repeatedly in tests.
 """
+
 import datetime
 import logging
 import os
@@ -160,6 +161,8 @@ def fake_tag() -> str:
     is_reproducible=True,
     repro_access_hours=3,
 )
+artifact_don_quixote.created_at -= datetime.timedelta(days=2)
+
 version_don_quixote_1 = ArtifactVersion(
     artifact=artifact_don_quixote,
     contents_urn=f"urn:trovi:contents:chameleon:{uuid4()}",
@@ -270,9 +273,9 @@ def generate_fake_artifact() -> list[models.Model]:
         ArtifactEvent(
             artifact_version=random.choice(artifact_versions),
             event_type=random.choice(ArtifactEvent.EventType.values),
-            event_origin=None
-            if fake.boolean(chance_of_getting_true=90)
-            else fake_user_urn(),
+            event_origin=(
+                None if fake.boolean(chance_of_getting_true=90) else fake_user_urn()
+            ),
         )
         for _ in range(random.randint(0, 40))
     ]
@@ -282,10 +285,12 @@ def _verified() -> dict[str, Union[bool, Optional[datetime.datetime]]]:
         verified = fake.boolean(chance_of_getting_true=20)
         return {
             "verified": verified,
-            "verified_at": None
-            if not verified
-            else fake.date_time_between(
-                datetime.date.min, datetime.date.max, timezone.utc
+            "verified_at": (
+                None
+                if not verified
+                else fake.date_time_between(
+                    datetime.date.min, datetime.date.max, timezone.utc
+                )
             ),
         }