Python

Skipping tests not explicitly requested with pytest

Problem

Pytest has nice facilities for running subsets of tests based on test names or markers added to tests. The one downside, however, is that to exclude a test a keyword or marker must always be given. What I would like, however, is to be able to run certain tests only if explicitly requested. The documentation shows using a custom command-line parameter to create a marker that does this, but it feels redundant with the existing -k keyword and -m marker facilities.

Solution (Partial)

With a helper function and ad-hoc parsing of the marker expression, I have been able to create a mark permits a test to run only if the marker is requested:

from collections import defaultdict

import pytest


def marker_requested(marker, markexpr=None):
    markexpr = markexpr or pytest.config.getoption('markexpr')
    # Ensure that we have a mark expression and that our marker is in it --
    #  otherwise marker_requested(marker="foo", markexpr="not bar") == True
    if not markexpr or marker not in markexpr.split():
        return False
    # This is essentially what _pytest.mark.matchmark does
    return eval(markexpr, {}, defaultdict(lambda: False, {marker: True}))
    

def skip_unless_mark_requested(marker):
    return pytest.mark.skipif(
            not marker_requested('foo'),
            reason='Marker "{}" required'.format(marker)
        )


skip_unless_foo_requested = skip_unless_mark_requested('foo')

@pytest.mark.foo
@skip_unless_foo_requested
def test_foo_really_foo():
    ...

What is missing, however, is automatically adding the requested marker itself to the test; this has to be done in addition to the skip_unless_... marker, which seems redundant.