From 60295135dd9fb0ccce830f239f70ca01f147a439 Mon Sep 17 00:00:00 2001
From: Christopher Krah <48338417+chrikrah@users.noreply.github.com>
Date: Mon, 12 Oct 2026 08:29:29 +0200
Subject: [PATCH] test(router): stop test_default_model_fallbacks leaking
 litellm.default_fallbacks

The litellm_module_fallbacks=True cases assigned litellm.default_fallbacks
directly and never put it back. isolate_litellm_globals does not reset that
global, so any later test in the same process that builds a Router without
default_fallbacks inherits ["my-good-model"]. In collection order that fails
test_has_default_fallbacks[False-False] and test_get_first_default_fallback
in test_router_helper_utils.py.

Set it through monkeypatch so it is restored at teardown.
---
 tests/unit/test_router/test_router_fallbacks.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/unit/test_router/test_router_fallbacks.py b/tests/unit/test_router/test_router_fallbacks.py
index 88d89696297..5ae0a83e8b2 100644
--- a/tests/unit/test_router/test_router_fallbacks.py
+++ b/tests/unit/test_router/test_router_fallbacks.py
@@ -77,14 +77,14 @@ async def test_async_fallbacks_streaming():
 @pytest.mark.parametrize("sync_mode", [True, False])
 @pytest.mark.parametrize("litellm_module_fallbacks", [True, False])
 @pytest.mark.asyncio
-async def test_default_model_fallbacks(sync_mode, litellm_module_fallbacks):
+async def test_default_model_fallbacks(sync_mode, litellm_module_fallbacks, monkeypatch: pytest.MonkeyPatch):
     """
     Related issue - https://github.com/BerriAI/litellm/issues/3623
 
     If model misconfigured, setup a default model for generic fallback
     """
     if litellm_module_fallbacks:
-        litellm.default_fallbacks = ["my-good-model"]
+        monkeypatch.setattr(litellm, "default_fallbacks", ["my-good-model"])
     router = Router(
         model_list=[
             {