code: def test_single_file(self, tmp_path: Path) -> None:
      fn = tmp_path / "foo.py"
      fn.touch()
      assert get_common_ancestor([fn]) == tmp_path
  
imports: import os
  from pathlib import Path
  from textwrap import dedent
  import pytest
  from _pytest.config import UsageError
  from _pytest.config.findpaths import get_common_ancestor
  from _pytest.config.findpaths import get_dirs_from_args
  from _pytest.config.findpaths import is_fs_root
  from _pytest.config.findpaths import load_config_dict_from_file
label_desc: Use image node_id 3 for calling the TestCommonAncestor obj's underlying member method code with example usage: obj.test_single_file(tmp_path) without return types