Why is there a random unexpected chdir on ctrl+c??

test.py

"""this test passes if you let it run, but fails assert_pwd if you ctrl-c"""
from __future__ import annotations

import contextlib
import typing
from os import chdir, environ, getcwd
from pathlib import Path
from time import sleep

from pytest import fixture

T = typing.TypeVar("T")
Generator = typing.Generator[T, None, None]  # py313/PEP696 shim


def assert_pwd(msg: object) -> Path:
    """double-check that $PWD stays accurate"""

    pwd = Path(environ["PWD"])
    cwd = Path.cwd()
    same = pwd.samefile(cwd)
    print("ASSERT_PWD", msg, "OK" if same else "FAIL!")
    if not same:
        print("   ", pwd)
        print("   ", cwd)
    assert pwd.samefile(cwd), (pwd, cwd)
    return pwd


@contextlib.contextmanager
def cd(
    dirname: Path,
) -> Generator[Path]:
    assert_pwd("cwd")
    oldpwd = environ["PWD"]

    environ["PWD"] = str(dirname)
    chdir(dirname)
    assert_pwd("cwd up")
    try:
        yield oldpwd
    finally:
        assert_pwd("cwd downing...")
        chdir(oldpwd)
        environ["PWD"] = oldpwd
    assert_pwd("cwd down")


@fixture
def cwd(tmp_path: Path) -> Generator[Path]:
    """prevent cross-test pollution of cwd"""
    with cd(tmp_path):
        yield tmp_path


def test(cwd):
    assert_pwd("sleepies")

    try:
        sleep(2)
    finally:
        assert_pwd("teardown")