Select and/or deselect tests that use a particular fixture?

Question

I see that there are some questions about conditionally skipping tests with certain fixtures: Is there a way to skip a pytest fixture? and Skip tests using a particular pytest fixture.

However I am looking for a straightforward way to select or deselect tests that use a particular fixture. I'd like to avoid manually marking all such tests, because the fixture might be used indirectly, and this is generally error-prone and not scalable.

Ideally, I'd like to be able to run something like pytest -m 'not uses_foo', and all tests that require the foo fixture would be deselected.

Again, this question is not about skipping the tests. I am specifically asking about a way to make them (de-)selectable as one might normally be able to do with marks.

Answer 1

I'm not aware of a builtin mechanism, but you can easily implement it yourself.

The pytest_collection_modifyitems hook is run after test collection, at which point all fixtures have been resolved. The names of all fixtures requested by a test can be retrieved via the fixturenames attribute. In the same hook, you can mark the tests with a skip marker or remove the tests you don't want to run entirely. If you want them to appear as deselected, you can call the pytest_deselected hook from this hook.

To make it configurable from the command line, you can use the pytest_addoption hook.

Example conftest.py:

import pytest

def pytest_addoption(parser):
    parser.addoption("--skip-fixtures", default=None)

def pytest_collection_modifyitems(config, items):
    skip_fixtures_opt = config.option.skip_fixtures
    if not skip_fixtures_opt:
        return

    skipped_fixtures = skip_fixtures_opt.split(",")
    selected = list(items)
    deselected = []

    for test_item in items:
        for fixture in skipped_fixtures:
            if fixture in test_item.fixturenames:
                selected.remove(test_item)
                deselected.append(test_item)

    items[:] = selected
    config.hook.pytest_deselected(items=deselected)

If you run pytest --skip-fixtures "foo,bar", all tests using foo or bar will be deselected. If you want to skip them instead, add a skip marker via test_item.add_marker(pytest.mark.skip("reason..."))