bug(tests): TestEnsureUserSystemdEnv fails on Python 3.12 — FakePath subclass ignores redirected path in __new__

[teyrebaz33]

Bug

tests/hermes_cli/test_gateway_service.py::TestEnsureUserSystemdEnv::test_sets_xdg_runtime_dir_when_missing fails on Python 3.12 / WSL2.

Root Cause

The test uses a FakePath subclass to redirect /run/user/42 to a temp directory:

class FakePath(type(RealPath())):
    def __new__(cls, *args):
        if p == "/run/user/42":
            return RealPath.__new__(cls, str(tmp_path))

In Python 3.12, PosixPath.__new__ ignores the path argument passed to RealPath.__new__ and re-initializes the internal path from the original string. So FakePath("/run/user/42").exists() returns False instead of True, and XDG_RUNTIME_DIR is never set.

Fix

Replace FakePath subclass with a direct monkeypatch on Path.exists:

monkeypatch.setattr(gateway_cli.Path, "exists", lambda self: str(self) == "/run/user/42")

This patches the method directly on the class used by the module under test, avoiding the Python 3.12 __new__ behavior entirely.

Evidence

FAILED tests/hermes_cli/test_gateway_service.py::TestEnsureUserSystemdEnv::test_sets_xdg_runtime_dir_when_missing
AssertionError: assert None == '/run/user/42'