A pytest fixture for detecting leaking file descriptors

debug_fd.py

import os
import pytest
import subprocess


def get_open_fds():
    cmd = f"lsof -p {os.getpid()}"
    result = subprocess.run(cmd.split(), capture_output=True)
    return {line.split()[-1] for line in result.stdout.splitlines()}


@pytest.fixture
def debug_fd():
    old_fds = get_open_fds()
    yield
    new_fds = get_open_fds()
    delta = new_fds - old_fds
    assert not delta