test: add ToolListCache caching coverage

Add a small unit test that validates ToolListCache caching semantics, deep-copy isolation, and retry/backoff behavior.

Made-with: Cursor

Author: Denis Megerle

tests/utils/test_tool_list_cache_on_cpu.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+# Copyright 2026 Bytedance Ltd. and/or its affiliates
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+import pytest
+
+import verl.tools.utils.tool_registry as tool_registry
+from verl.tools.utils.tool_registry import ToolListCache
+
+
+@dataclass(frozen=True)
+class _DummyTool:
+    name: str
+
+
+def test_tool_list_cache_returns_empty_for_none():
+    ToolListCache._cache.clear()
+    assert ToolListCache.get_tool_list(None) == []
+
+
+def test_tool_list_cache_caches_and_deepcopies(monkeypatch: pytest.MonkeyPatch):
+    ToolListCache._cache.clear()
+
+    calls: list[tuple[str, float | None]] = []
+
+    def _fake_init(tools_config_file: str, mcp_init_timeout_s: float | None = None):
+        calls.append((tools_config_file, mcp_init_timeout_s))
+        return [_DummyTool(name="t1")]
+
+    monkeypatch.setattr(tool_registry, "initialize_tools_from_config", _fake_init)
+    monkeypatch.setenv("VERL_TOOL_CACHE_INIT_TIMEOUT_S", "12")
+
+    out1 = ToolListCache.get_tool_list("dummy.yaml")
+    out2 = ToolListCache.get_tool_list("dummy.yaml")
+
+    assert calls == [("dummy.yaml", 12.0)]
+    assert out1 == out2
+    assert out1 is not out2
+    assert out1[0] is not out2[0]
+
+
+def test_tool_list_cache_retries_before_failing(monkeypatch: pytest.MonkeyPatch):
+    ToolListCache._cache.clear()
+
+    attempts = {"n": 0}
+
+    def _fake_init(tools_config_file: str, mcp_init_timeout_s: float | None = None):
+        attempts["n"] += 1
+        if attempts["n"] == 1:
+            raise RuntimeError("boom")
+        return [_DummyTool(name="t1")]
+
+    sleeps: list[float] = []
+
+    monkeypatch.setattr(tool_registry, "initialize_tools_from_config", _fake_init)
+    monkeypatch.setattr(tool_registry.time, "sleep", lambda s: sleeps.append(float(s)))
+    monkeypatch.setenv("VERL_TOOL_CACHE_INIT_RETRIES", "2")
+    monkeypatch.setenv("VERL_TOOL_CACHE_INIT_TIMEOUT_S", "0.5")
+    monkeypatch.setenv("VERL_TOOL_CACHE_INIT_BACKOFF_BASE_S", "0.01")
+    monkeypatch.setenv("VERL_TOOL_CACHE_INIT_BACKOFF_MAX_S", "0.01")
+
+    out = ToolListCache.get_tool_list("dummy.yaml")
+
+    assert out == [_DummyTool(name="t1")]
+    assert attempts["n"] == 2
+    assert sleeps == [0.01]