unsloth/tests/python/test_install_python_stack.py

"""Tests for install_python_stack._build_uv_cmd torch-backend handling."""

from __future__ import annotations

import importlib
import os
import sys
from pathlib import Path
from unittest import mock

import pytest

STUDIO_DIR = Path(__file__).resolve().parents[2] / "studio"
sys.path.insert(0, str(STUDIO_DIR))

import install_python_stack as ips


class TestBuildUvCmdTorchBackend:
    """Verify _build_uv_cmd only adds --torch-backend when UV_TORCH_BACKEND is set."""

    def _call(self, args: tuple[str, ...] = ()) -> list[str]:
        return ips._build_uv_cmd(args)

    def test_default_no_torch_backend(self):
        """Without UV_TORCH_BACKEND env var, no --torch-backend flag."""
        env = os.environ.copy()
        env.pop("UV_TORCH_BACKEND", None)
        with mock.patch.dict(os.environ, env, clear = True):
            cmd = self._call(("somepackage",))
        assert not any(
            a.startswith("--torch-backend") for a in cmd
        ), f"--torch-backend should not appear by default, got: {cmd}"

    def test_uv_torch_backend_auto(self):
        """UV_TORCH_BACKEND=auto adds --torch-backend=auto."""
        with mock.patch.dict(os.environ, {"UV_TORCH_BACKEND": "auto"}):
            cmd = self._call(("somepackage",))
        assert "--torch-backend=auto" in cmd

    def test_uv_torch_backend_cpu(self):
        """UV_TORCH_BACKEND=cpu adds --torch-backend=cpu."""
        with mock.patch.dict(os.environ, {"UV_TORCH_BACKEND": "cpu"}):
            cmd = self._call(("somepackage",))
        assert "--torch-backend=cpu" in cmd

    def test_uv_torch_backend_empty(self):
        """UV_TORCH_BACKEND="" (empty string) should NOT add --torch-backend."""
        with mock.patch.dict(os.environ, {"UV_TORCH_BACKEND": ""}):
            cmd = self._call(("somepackage",))
        assert not any(
            a.startswith("--torch-backend") for a in cmd
        ), f"Empty UV_TORCH_BACKEND should not add flag, got: {cmd}"