import pytest

def pytest_addoption(parser):

    parser.addoption(

        "--runslow", action="store_true", default=False, help="run slow tests"

    )

def pytest_collection_modifyitems(config, items):

    if config.getoption("--runslow"):

        # --runslow given in cli: do not skip slow tests

        return

    skip_slow = pytest.mark.skip(reason="need --runslow option to run")

    for item in items:

        if "slow" in item.keywords:

            item.add_marker(skip_slow)