test: 补充知识处理、检索与 Agent 回归用例

覆盖切块、向量检索、工具调用和历史预算；模型相关用例使用桩。

backend/tests/knowledge/test_rechunk_knowledge_transaction.py

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+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+scripts.rechunk_knowledge against a real SQLAlchemy connection.
+
+The other script tests mock the connection, which hides transaction
+semantics: SQLAlchemy 2.x autobegins a transaction on the first SELECT, and
+``Connection.begin()`` then raises ``InvalidRequestError`` until that
+transaction is committed or rolled back. ``process_table`` runs two SELECTs
+before ``replace_row`` calls ``conn.begin()``, so every row fails.
+"""
+
+import hashlib
+from unittest.mock import MagicMock, patch
+
+import pytest
+from sqlalchemy import create_engine, event, text
+
+from scripts import rechunk_knowledge as script
+
+
+@pytest.fixture
+def conn():
+    engine = create_engine("sqlite://")
+
+    @event.listens_for(engine, "connect")
+    def _setup(dbapi_conn, _):
+        dbapi_conn.create_function("md5", 1, lambda s: hashlib.md5(s.encode()).hexdigest())
+        dbapi_conn.execute("ATTACH DATABASE ':memory:' AS ai")
+        dbapi_conn.execute(
+            'CREATE TABLE ai."d_o" (id TEXT PRIMARY KEY, name TEXT, meta_data TEXT, filters TEXT, '
+            "content TEXT, embedding TEXT, usage TEXT, content_hash TEXT)"
+        )
+
+    with engine.connect() as conn:
+        conn.execute(
+            text('INSERT INTO ai."d_o" (id, name, content, meta_data, filters) VALUES (:id, :n, :c, NULL, NULL)'),
+            {"id": "https://x.com/p", "n": "https://x.com", "c": "para. " * 300},
+        )
+        conn.commit()
+        yield conn
+
+
+def test_process_table_replaces_row_on_a_real_connection(conn):
+    embedder = MagicMock()
+    embedder.get_embedding_and_usage.return_value = ([0.5, 0.5], None)
+
+    # ``id = ANY(:ids)`` is Postgres-only; the collision check is not what is under test.
+    with patch.object(script, "existing_ids", lambda *_: []):
+        report = script.process_table(conn, "d_o", embedder, size=300, dry_run=False)
+
+    assert report.failed == 0, "replace_row must work after the SELECTs that precede it"
+    ids = [r.id for r in conn.execute(text('SELECT id FROM ai."d_o" ORDER BY length(id), id')).fetchall()]
+    assert ids and ids[0] == "https://x.com/p::1" and "https://x.com/p" not in ids
+    assert len(ids) == report.chunks