test(proxy): cover list-valued fallback preflight

Author: Duxl-Ai

tests/test_litellm/proxy/test_blocked_model_list_fallback_preflight.py

@@ -0,0 +1,80 @@
+from unittest.mock import AsyncMock
+
+import pytest
+
+from litellm.proxy.route_llm_request import _get_available_fallback_request
+
+
+class _ListFallbackRouter:
+    max_fallbacks = 5
+    model_group_alias = {}
+
+    def __init__(self, fallbacks, healthy_models):
+        self.fallbacks = fallbacks
+        self.healthy_models = set(healthy_models)
+        self.model_list = [
+            {"model_info": {"id": "primary-deployment"}},
+            {"model_info": {"id": "first-deployment"}},
+            {"model_info": {"id": "second-deployment"}},
+            {"model_info": {"id": "later-deployment"}},
+        ]
+        self.async_pre_routing_hook = AsyncMock(return_value=None)
+
+    async def async_get_healthy_deployments(self, *, model, **kwargs):
+        if model not in self.healthy_models:
+            return []
+        deployment_id = {
+            "first-model": "first-deployment",
+            "second-model": "second-deployment",
+            "later-model": "later-deployment",
+        }[model]
+        return [{"model_info": {"id": deployment_id}}]
+
+
+@pytest.mark.asyncio
+async def test_list_valued_direct_fallback_uses_first_healthy_candidate():
+    router = _ListFallbackRouter(
+        fallbacks=[{"model": ["first-model", "second-model"], "temperature": 0.2}],
+        healthy_models={"second-model"},
+    )
+
+    request = await _get_available_fallback_request(
+        llm_router=router,
+        model_name="blocked-model",
+        team_id=None,
+        request_data={"messages": [{"role": "user", "content": "hello"}]},
+    )
+
+    assert request is not None
+    assert request["model"] == "second-model"
+    assert request["temperature"] == 0.2
+    assert request["fallbacks"] == []
+    assert [call.kwargs["model"] for call in router.async_pre_routing_hook.await_args_list] == [
+        "first-model",
+        "second-model",
+    ]
+
+
+@pytest.mark.asyncio
+async def test_list_valued_direct_fallback_preserves_remaining_candidates_in_trusted_tail():
+    router = _ListFallbackRouter(
+        fallbacks=[
+            {"model": ["first-model", "second-model"], "temperature": 0.2},
+            "later-model",
+        ],
+        healthy_models={"first-model", "second-model", "later-model"},
+    )
+
+    request = await _get_available_fallback_request(
+        llm_router=router,
+        model_name="blocked-model",
+        team_id=None,
+        request_data={"messages": [{"role": "user", "content": "hello"}]},
+    )
+
+    assert request is not None
+    assert request["model"] == "first-model"
+    assert request["fallbacks"] == [
+        {"model": "second-model", "temperature": 0.2},
+        "later-model",
+    ]