test(model_prices): type the Mistral cache-read helpers and check the backup registry too

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

tests/test_litellm/test_model_prices_schema.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 import importlib.util
 import json
 import re
+from collections.abc import Mapping
 from pathlib import Path
 from types import MappingProxyType
 from typing import Final
@@ -276,29 +277,40 @@ def test_every_bedrock_openai_gpt_row_advertises_xhigh(prices: dict):
     assert missing == []
 
 
-def is_active_priced_mistral_chat_row(name: str, entry: dict) -> bool:
+def is_active_priced_mistral_chat_row(name: str, entry: Mapping[str, object]) -> bool:
+    input_cost: Final = entry.get("input_cost_per_token")
     return (
         name.startswith("mistral/")
         and entry.get("mode") == "chat"
         and entry.get("deprecation_date") is None
-        and (entry.get("input_cost_per_token") or 0) > 0
+        and isinstance(input_cost, (int, float))
+        and input_cost > 0
     )
 
 
-def test_active_mistral_chat_rows_price_cache_reads_below_input(prices: dict):
+def cache_read_is_tenth_of_input(entry: Mapping[str, object]) -> bool:
+    cache_read: Final = entry.get("cache_read_input_token_cost")
+    input_cost: Final = entry.get("input_cost_per_token")
+    return (
+        isinstance(cache_read, float)
+        and isinstance(input_cost, (int, float))
+        and 0 < cache_read < input_cost
+        and cache_read == pytest.approx(input_cost / 10)
+    )
+
+
+@pytest.mark.parametrize("path", (PRICES_PATH, BACKUP_PRICES_PATH), ids=("main", "backup"))
+def test_active_mistral_chat_rows_price_cache_reads_below_input(path: Path):
     """A Mistral chat row without a cache-read rate bills cached prompt tokens at zero, so every
     active priced row must carry one, and it must be cheaper than a fresh input token. Mistral
     bills cached tokens at 10% of the input price for every model (docs.mistral.ai/studio/
     conversations/advanced/prompt-caching, read 2026-09-18), so the ratio is checked as well."""
+    rows: Mapping[str, object] = json.loads(path.read_text())
     drifted: Final = [
-        f"{name}: cache_read={entry.get('cache_read_input_token_cost')} input={entry['input_cost_per_token']}"
-        for name, entry in prices.items()
+        f"{name}: cache_read={entry.get('cache_read_input_token_cost')} input={entry.get('input_cost_per_token')}"
+        for name, entry in rows.items()
         if isinstance(entry, dict)
         and is_active_priced_mistral_chat_row(name, entry)
-        and not (
-            isinstance(entry.get("cache_read_input_token_cost"), float)
-            and 0 < entry["cache_read_input_token_cost"] < entry["input_cost_per_token"]
-            and entry["cache_read_input_token_cost"] == pytest.approx(entry["input_cost_per_token"] / 10)
-        )
+        and not cache_read_is_tenth_of_input(entry)
     ]
     assert drifted == []