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/core/test_widget_channels.py

@@ -0,0 +1,43 @@
+"""
+Copyright 2024-2026 ReplyPier
+
+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.
+"""
+
+import pytest
+
+from app.channels.constants import WIDGET_CHANNELS, is_widget_channel
+
+
+class TestIsWidgetChannel:
+    @pytest.mark.parametrize("channel", ["web", "shopify"])
+    def test_our_own_widget_surfaces(self, channel):
+        assert is_widget_channel(channel) is True
+
+    @pytest.mark.parametrize("channel", [None, ""])
+    def test_absent_channel_means_the_widget(self, channel):
+        """Sessions predating the column, and anything that omits it."""
+        assert is_widget_channel(channel) is True
+
+    @pytest.mark.parametrize(
+        "channel",
+        ["telegram", "whatsapp", "messenger", "instagram", "slack", "email", "sms", "line"],
+    )
+    def test_external_platforms_are_not_the_widget(self, channel):
+        assert is_widget_channel(channel) is False
+
+    def test_shopify_is_a_widget_channel(self):
+        """The whole point: labelling Shopify separately must not cost it the
+        widget features that 'web' gets — the rating prompt above all."""
+        assert "shopify" in WIDGET_CHANNELS
+        assert is_widget_channel("shopify") is True