aurweb.testing.setup_test_db: Expunge objects

This is needed to avoid redundant objects in SQLAlchemy's
IdentityMap, since we pass a direct .execute to delete
the tables passed in. Additionally, remove our engine.connect()
call in favor of relying on the already-established Session.
Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/testing/__init__.py

@@ -21,10 +21,12 @@ def setup_test_db(*args):
         test_tables = ["Users", "Sessions"];
         setup_test_db(*test_tables)
     """
-    engine = aurweb.db.get_engine()
-    conn = engine.connect()
+    # Make sure that we've grabbed the engine before using the session.
+    aurweb.db.get_engine()
 
     tables = list(args)
     for table in tables:
-        conn.execute(f"DELETE FROM {table}")
-    conn.close()
+        aurweb.db.session.execute(f"DELETE FROM {table}")
+
+    # Expunge all objects from SQLAlchemy's IdentityMap.
+    aurweb.db.session.expunge_all()