diff --git a/.gitea/workflows/build.yaml b/.gitea/workflows/build.yaml
index 10d48eb..ff67c48 100644
--- a/.gitea/workflows/build.yaml
+++ b/.gitea/workflows/build.yaml
@@ -166,6 +166,8 @@ jobs:
 
             echo "Waiting for backend to be ready..."
             sleep 10
+            echo "Resetting MongoDB test database..."
+            docker-compose -f docker-compose.test.yml exec -T chores-test-app-backend python -c "from db.db import reset_mongo_db; reset_mongo_db()"
             echo "Seeding test user..."
             docker-compose -f docker-compose.test.yml exec -T chores-test-app-backend python scripts/seed_test_user.py
             echo "Creating admin user..."
diff --git a/backend/db/db.py b/backend/db/db.py
index 5bfb2e6..07090b7 100644
--- a/backend/db/db.py
+++ b/backend/db/db.py
@@ -579,29 +579,38 @@ def ensure_mongodb_indexes(client=None, db_name=None):
             coll.create_index(keys, **kwargs)
 
 
-# Clear test data at import time so tests start with a clean slate.
-if os.environ.get('DB_ENV', 'prod') == 'test':
-    if USE_MONGODB:
-        # Drop the entire MongoDB test database for a fresh start. Only do this
-        # for clearly test/e2e database names as a safety guard.
-        if _mongo_db_name and _mongo_db_name.endswith(('_test', '_e2e')):
-            get_mongo_client().drop_database(_mongo_db_name)
-    else:
-        child_db.truncate()
-        task_db.truncate()
-        routine_db.truncate()
-        routine_items_db.truncate()
-        routine_schedules_db.truncate()
-        routine_extensions_db.truncate()
-        reward_db.truncate()
-        image_db.truncate()
-        pending_reward_db.truncate()
-        pending_confirmations_db.truncate()
-        users_db.truncate()
-        tracking_events_db.truncate()
-        child_overrides_db.truncate()
-        chore_schedules_db.truncate()
-        task_extensions_db.truncate()
-        refresh_tokens_db.truncate()
-        push_subscriptions_db.truncate()
-        digest_action_tokens_db.truncate()
+# Clear test collections at import time so tests start with a clean slate.
+# Only TinyDB path — MongoDB cleanup is handled explicitly via reset_mongo_db().
+if os.environ.get('DB_ENV', 'prod') == 'test' and not USE_MONGODB:
+    child_db.truncate()
+    task_db.truncate()
+    routine_db.truncate()
+    routine_items_db.truncate()
+    routine_schedules_db.truncate()
+    routine_extensions_db.truncate()
+    reward_db.truncate()
+    image_db.truncate()
+    pending_reward_db.truncate()
+    pending_confirmations_db.truncate()
+    users_db.truncate()
+    tracking_events_db.truncate()
+    child_overrides_db.truncate()
+    chore_schedules_db.truncate()
+    task_extensions_db.truncate()
+    refresh_tokens_db.truncate()
+    push_subscriptions_db.truncate()
+    digest_action_tokens_db.truncate()
+
+
+def reset_mongo_db():
+    """Drop the MongoDB test/e2e database for a totally fresh slate.
+
+    Only acts on database names ending with ``_test`` or ``_e2e`` as a
+    safety guard against accidentally dropping production data.  Call this
+    once at the start of a test session or deployment seed step.
+    """
+    if not USE_MONGODB:
+        return
+    if not _mongo_db_name or not _mongo_db_name.endswith(('_test', '_e2e')):
+        return
+    get_mongo_client().drop_database(_mongo_db_name)
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
index ba97ced..2e84999 100644
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -24,7 +24,8 @@ def set_test_db_env():
     os.environ['MONGO_URI'] = 'mongomock'
     os.environ['SECRET_KEY'] = TEST_SECRET_KEY
     os.environ['REFRESH_TOKEN_EXPIRY_DAYS'] = str(TEST_REFRESH_TOKEN_EXPIRY_DAYS)
-    # Ensure indexes are created once for the test session.  This is safe to
-    # call repeatedly because MongoDB treats index creation as idempotent.
-    from db.db import ensure_mongodb_indexes
+    # Drop the MongoDB test database once at the start of the session so every
+    # test begins from a clean slate.  Indexes are recreated afterward.
+    from db.db import reset_mongo_db, ensure_mongodb_indexes
+    reset_mongo_db()
     ensure_mongodb_indexes()