refactor: migrate high-risk write transactions

tests/test_agent_chat_transaction.py

@@ -0,0 +1,92 @@
+"""Agent 会话删除的请求级事务边界测试。"""
+
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, Mock
+
+import pytest
+
+from app.application.messaging.chat import AgentChatService
+
+
+def _principal() -> SimpleNamespace:
+    """构造拥有目标会话的普通用户。"""
+    return SimpleNamespace(id=1, name="alice", is_superuser=False)
+
+
+def _chat() -> SimpleNamespace:
+    """构造应用服务投影所需的最小会话记录。"""
+    return SimpleNamespace(
+        id=9,
+        session_id="session-9",
+        client_session_id=None,
+        title="事务会话",
+        channel=None,
+        source=None,
+        user_id="1",
+        username="alice",
+        original_chat_id=None,
+        message_count=0,
+        created_at=None,
+        updated_at=None,
+        display_messages=[],
+    )
+
+
+@pytest.mark.asyncio
+async def test_delete_stages_then_commits_once() -> None:
+    """有权限的会话删除只能由 Service 在暂存成功后提交一次。"""
+    calls: list[str] = []
+    repository = Mock()
+    repository.async_get = AsyncMock(return_value=_chat())
+    repository.async_stage_delete = AsyncMock(
+        side_effect=lambda **_kwargs: calls.append("stage") or True
+    )
+    unit_of_work = Mock()
+    unit_of_work.commit = AsyncMock(
+        side_effect=lambda: calls.append("commit")
+    )
+    unit_of_work.rollback = AsyncMock()
+    service = AgentChatService(repository, unit_of_work)
+
+    assert await service.delete("session-9", _principal()) is True
+
+    assert calls == ["stage", "commit"]
+    unit_of_work.rollback.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_delete_rolls_back_flush_failure() -> None:
+    """暂存删除失败必须回滚并传播原异常。"""
+    error = RuntimeError("flush failed")
+    repository = Mock()
+    repository.async_get = AsyncMock(return_value=_chat())
+    repository.async_stage_delete = AsyncMock(side_effect=error)
+    unit_of_work = Mock()
+    unit_of_work.commit = AsyncMock()
+    unit_of_work.rollback = AsyncMock()
+    service = AgentChatService(repository, unit_of_work)
+
+    with pytest.raises(RuntimeError) as raised:
+        await service.delete("session-9", _principal())
+
+    assert raised.value is error
+    unit_of_work.commit.assert_not_awaited()
+    unit_of_work.rollback.assert_awaited_once_with()
+
+
+@pytest.mark.asyncio
+async def test_delete_missing_chat_does_not_open_write_transaction() -> None:
+    """会话不存在时保持旧 False 返回，且不执行 stage 或 commit。"""
+    repository = Mock()
+    repository.async_get = AsyncMock(return_value=None)
+    repository.async_stage_delete = AsyncMock()
+    unit_of_work = Mock()
+    unit_of_work.commit = AsyncMock()
+    unit_of_work.rollback = AsyncMock()
+    service = AgentChatService(repository, unit_of_work)
+
+    assert await service.delete("missing", _principal()) is False
+
+    repository.async_stage_delete.assert_not_awaited()
+    unit_of_work.commit.assert_not_awaited()
+    unit_of_work.rollback.assert_not_awaited()