conftest.py

import pytest
import sys


@pytest.fixture(scope="function")
def argv_handler(request):
    """This fixture restores sys.argv and sys.stdin after tests.
    """
    _argv_stored = sys.argv
    _stdin_stored = sys.stdin

    def teardown():
        sys.argv = _argv_stored
        sys.stdin = _stdin_stored
    request.addfinalizer(teardown)