Add LangChain vm_run wrapper example

tests/test_langchain_example.py

@@ -0,0 +1,64 @@
+from __future__ import annotations
+
+import importlib.util
+import sys
+from pathlib import Path
+from types import ModuleType
+from typing import Any, cast
+
+import pytest
+
+
+def _load_langchain_example_module() -> ModuleType:
+    path = Path("examples/langchain_vm_run.py")
+    spec = importlib.util.spec_from_file_location("langchain_vm_run", path)
+    if spec is None or spec.loader is None:
+        raise AssertionError("failed to load LangChain example module")
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+def test_langchain_example_delegates_to_pyro(monkeypatch: pytest.MonkeyPatch) -> None:
+    module = _load_langchain_example_module()
+    monkeypatch.setattr(
+        module,
+        "Pyro",
+        lambda: type(
+            "StubPyro",
+            (),
+            {
+                "run_in_vm": staticmethod(
+                    lambda **kwargs: {"exit_code": 0, "stdout": kwargs["command"], "network": False}
+                )
+            },
+        )(),
+    )
+    result = module.run_vm_run_tool(
+        profile="debian-git",
+        command="git --version",
+        vcpu_count=1,
+        mem_mib=1024,
+    )
+    assert "git --version" in result
+
+
+def test_langchain_example_builds_vm_run_tool(monkeypatch: pytest.MonkeyPatch) -> None:
+    module = _load_langchain_example_module()
+    fake_langchain_tools = ModuleType("langchain_core.tools")
+
+    def fake_tool(name: str) -> Any:
+        def decorator(fn: Any) -> Any:
+            fn.name = name
+            return fn
+
+        return decorator
+
+    cast(Any, fake_langchain_tools).tool = fake_tool
+    fake_langchain_core = ModuleType("langchain_core")
+    monkeypatch.setitem(sys.modules, "langchain_core", fake_langchain_core)
+    monkeypatch.setitem(sys.modules, "langchain_core.tools", fake_langchain_tools)
+
+    tool = module.build_langchain_vm_run_tool()
+
+    assert tool.name == "vm_run"