chore: import upstream snapshot with attribution

tests/test_cache_encoding.py

@@ -0,0 +1,65 @@
+"""Regression tests for cross-platform cache encoding."""
+
+from __future__ import annotations
+
+import json
+import time
+
+import whichllm.models.benchmark as benchmark_mod
+import whichllm.models.cache as cache_mod
+
+
+class _ReadableCacheFile:
+    def __init__(self, payload: dict):
+        self.payload = payload
+        self.encoding = None
+
+    def exists(self) -> bool:
+        return True
+
+    def read_text(self, *, encoding: str | None = None) -> str:
+        self.encoding = encoding
+        return json.dumps(self.payload, ensure_ascii=False)
+
+
+class _WritableCacheFile:
+    def __init__(self):
+        self.encoding = None
+        self.text = None
+
+    def write_text(self, text: str, *, encoding: str | None = None) -> int:
+        self.encoding = encoding
+        self.text = text
+        return len(text)
+
+
+def test_model_cache_reads_and_writes_utf8(monkeypatch, tmp_path):
+    reader = _ReadableCacheFile(
+        {"cached_at": time.time(), "models": [{"id": "test/Omega-Ω"}]}
+    )
+    monkeypatch.setattr(cache_mod, "CACHE_FILE", reader)
+    assert cache_mod.load_cache() == [{"id": "test/Omega-Ω"}]
+    assert reader.encoding == "utf-8"
+
+    writer = _WritableCacheFile()
+    monkeypatch.setattr(cache_mod, "CACHE_DIR", tmp_path)
+    monkeypatch.setattr(cache_mod, "CACHE_FILE", writer)
+    cache_mod.save_cache([{"id": "test/Omega-Ω"}])
+    assert writer.encoding == "utf-8"
+    assert "Ω" in writer.text
+
+
+def test_benchmark_cache_reads_and_writes_utf8(monkeypatch, tmp_path):
+    reader = _ReadableCacheFile(
+        {"cached_at": time.time(), "scores": {"test/Omega-Ω": 1.0}}
+    )
+    monkeypatch.setattr(benchmark_mod, "BENCHMARK_CACHE", reader)
+    assert benchmark_mod.load_benchmark_cache() == {"test/Omega-Ω": 1.0}
+    assert reader.encoding == "utf-8"
+
+    writer = _WritableCacheFile()
+    monkeypatch.setattr(benchmark_mod, "CACHE_DIR", tmp_path)
+    monkeypatch.setattr(benchmark_mod, "BENCHMARK_CACHE", writer)
+    benchmark_mod.save_benchmark_cache({"test/Omega-Ω": 1.0})
+    assert writer.encoding == "utf-8"
+    assert "Ω" in writer.text