fix(tests): stabilize CUDA MPS CLI tests on macOS

tests/training/test_cuda_mps_cli.py

@@ -8,6 +8,7 @@
 import socket
 import stat
 import tempfile
+from collections.abc import Iterator
 from pathlib import Path
 from types import SimpleNamespace
 from typing import Any
@@ -56,11 +57,18 @@ def torch_with_uuid(uuid: str = GPU_A) -> Any:
 
 
 @pytest.fixture
-def linux_host(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> Path:
+def short_temp_path() -> Iterator[Path]:
+    temporary_root = Path("/tmp").resolve()
+    with tempfile.TemporaryDirectory(prefix="ucmps-", dir=temporary_root) as raw:
+        yield Path(raw)
+
+
+@pytest.fixture
+def linux_host(monkeypatch: pytest.MonkeyPatch, short_temp_path: Path) -> Path:
     fake_platform(monkeypatch)
-    root = tmp_path / "registry"
-    monkeypatch.setenv("HOME", str(tmp_path / "home"))
-    (tmp_path / "home").mkdir()
+    root = short_temp_path / "registry"
+    monkeypatch.setenv("HOME", str(short_temp_path / "home"))
+    (short_temp_path / "home").mkdir()
     return root
 
 
@@ -137,9 +145,11 @@ def test_missing_selector_rejects_ambiguous_multi_gpu_host() -> None:
         mps.resolve_topology(None, run_command=fake_run())
 
 
-def test_start_rejects_task_per_gpu_until_lease_contract_lands() -> None:
+def test_start_rejects_task_per_gpu_until_lease_contract_lands(
+    linux_host: Path,
+) -> None:
     with pytest.raises(mps.CudaMpsError, match="current support is single_gpu"):
-        mps.start_daemon("all", root=Path("/unused"), run_command=fake_run())
+        mps.start_daemon("all", root=linux_host, run_command=fake_run())
 
 
 def test_status_is_read_only_and_reports_compatible_topology_modes(
@@ -366,7 +376,7 @@ def test_default_daemon_name_uses_complete_uuid() -> None:
 
 
 def test_start_daemon_rejects_long_unix_socket_path(linux_host: Path) -> None:
-    long_dir = linux_host / ("x" * 96)
+    long_dir = linux_host / ("x" * 200)
 
     with pytest.raises(mps.CudaMpsError, match="MPS control socket path is too long"):
         mps.start_daemon(
@@ -380,9 +390,9 @@ def test_start_daemon_rejects_long_unix_socket_path(linux_host: Path) -> None:
 
 
 def test_start_daemon_recovers_only_inert_failed_control_artifacts(
-    linux_host: Path, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    linux_host: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
-    short_root = tmp_path.parent / "u"
+    short_root = linux_host.parent / "u"
     monkeypatch.setattr(mps.tempfile, "gettempdir", lambda: str(short_root))
     monkeypatch.setattr(mps.shutil, "which", lambda _name: "/fake/bin/nvidia-cuda-mps-control")
     pipe_dir = short_root / "p" / "prod" / "pipe"
@@ -410,10 +420,10 @@ def test_start_daemon_recovers_only_inert_failed_control_artifacts(
 
 
 def test_start_daemon_failure_reports_control_log_and_cleans_artifacts(
-    linux_host: Path, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    linux_host: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
     monkeypatch.setattr(mps.shutil, "which", lambda _name: "/fake/bin/nvidia-cuda-mps-control")
-    short_root = tmp_path.parent / "u2"
+    short_root = linux_host.parent / "u2"
     monkeypatch.setattr(mps.tempfile, "gettempdir", lambda: str(short_root))
     pipe_dir = short_root / "p" / "prod" / "pipe"
     log_dir = short_root / "p" / "prod" / "log"
@@ -442,58 +452,60 @@ def run(command: list[str], **kwargs: Any) -> Completed:
     assert not (pipe_dir / "control_lock").exists()
 
 
-def test_default_runtime_recovers_orphan_control_sockets() -> None:
-    with tempfile.TemporaryDirectory() as raw:
-        root = Path(raw)
-        monkeypatch_root = root / "tmp"
-        runtime = monkeypatch_root / "uni-cumps" / "gpu-test" / "pipe"
-        runtime.mkdir(parents=True)
-        control = runtime / "control"
-        # Create actual socket nodes like NVIDIA leaves behind.
-        socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(control))
-        socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(runtime / "control_privileged"))
+def test_default_runtime_recovers_orphan_control_sockets(
+    short_temp_path: Path,
+) -> None:
+    root = short_temp_path
+    monkeypatch_root = root / "tmp"
+    runtime = monkeypatch_root / "uni-cumps" / "gpu-test" / "pipe"
+    runtime.mkdir(parents=True)
+    control = runtime / "control"
+    # Create actual socket nodes like NVIDIA leaves behind.
+    socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(control))
+    socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(runtime / "control_privileged"))
 
-        with pytest.MonkeyPatch.context() as monkeypatch:
-            monkeypatch.setattr(mps.tempfile, "gettempdir", lambda: str(monkeypatch_root))
-            root_path = mps._default_runtime_root("gpu-test")
-            mps._remove_orphan_default_control_sockets(root_path / "pipe")
+    with pytest.MonkeyPatch.context() as monkeypatch:
+        monkeypatch.setattr(mps.tempfile, "gettempdir", lambda: str(monkeypatch_root))
+        root_path = mps._default_runtime_root("gpu-test")
+        mps._remove_orphan_default_control_sockets(root_path / "pipe")
 
-        assert not control.exists()
-        assert not (runtime / "control_privileged").exists()
+    assert not control.exists()
+    assert not (runtime / "control_privileged").exists()
 
 
 def test_default_runtime_preserves_live_control_with_stale_pid_file(
     monkeypatch: pytest.MonkeyPatch,
+    short_temp_path: Path,
 ) -> None:
-    with tempfile.TemporaryDirectory() as raw:
-        runtime = Path(raw) / "uni-cumps" / "gpu-test" / "pipe"
-        runtime.mkdir(parents=True)
-        (runtime / "nvidia-cuda-mps-control.pid").write_text("4242\n", encoding="utf-8")
-        control = runtime / "control"
-        socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(control))
-
-        monkeypatch.setattr(mps, "_proc_stat", live_proc_stat())
-        monkeypatch.setattr(
-            mps,
-            "_process_name_is_alive",
-            lambda pid, name: pid == 4242 and name.startswith("nvidia"),
-        )
-        mps._remove_orphan_default_control_sockets(runtime)
+    runtime = short_temp_path / "uni-cumps" / "gpu-test" / "pipe"
+    runtime.mkdir(parents=True)
+    (runtime / "nvidia-cuda-mps-control.pid").write_text("4242\n", encoding="utf-8")
+    control = runtime / "control"
+    socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(control))
 
-        assert control.exists()
+    monkeypatch.setattr(mps, "_proc_stat", live_proc_stat())
+    monkeypatch.setattr(
+        mps,
+        "_process_name_is_alive",
+        lambda pid, name: pid == 4242 and name.startswith("nvidia"),
+    )
+    mps._remove_orphan_default_control_sockets(runtime)
+
+    assert control.exists()
 
 
-def test_default_runtime_removes_orphan_socket_with_stale_pid_file() -> None:
-    with tempfile.TemporaryDirectory() as raw:
-        runtime = Path(raw) / "uni-cumps" / "gpu-test" / "pipe"
-        runtime.mkdir(parents=True)
-        (runtime / "nvidia-cuda-mps-control.pid").write_text("99999999\n", encoding="utf-8")
-        control = runtime / "control"
-        socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(control))
+def test_default_runtime_removes_orphan_socket_with_stale_pid_file(
+    short_temp_path: Path,
+) -> None:
+    runtime = short_temp_path / "uni-cumps" / "gpu-test" / "pipe"
+    runtime.mkdir(parents=True)
+    (runtime / "nvidia-cuda-mps-control.pid").write_text("99999999\n", encoding="utf-8")
+    control = runtime / "control"
+    socket.socket(socket.AF_UNIX, socket.SOCK_STREAM).bind(str(control))
 
-        mps._remove_orphan_default_control_sockets(runtime)
+    mps._remove_orphan_default_control_sockets(runtime)
 
-        assert not control.exists()
+    assert not control.exists()
 
 
 def test_start_daemon_refuses_existing_unmanaged_control_path(