fix env variables exposure

tests/test_research_tools.py

@@ -140,6 +140,12 @@ class TestFormatResults:
 
 
 class TestSearchSearxng:
+    @pytest.fixture(autouse=True)
+    def mock_searxng_url(self) -> "Generator[None, None, None]":
+        from typing import Generator
+        with patch("gitea.tools.research_tools._SEARXNG_URL", "http://localhost"):
+            yield
+
     def _make_searxng_response(self, results: list[dict]) -> MagicMock:
         mock_resp = MagicMock()
         mock_resp.json.return_value = {"results": results}