Unit testing a function from conftest.py

[jandom]

This is a very basic question but I wasn't able to find a relevant answer anywhere here

My conftest.py has the helper inside, to auto-apply some markers

def pytest_collection_modifyitems(items):
    for item in items:
        if 'foo' in item.parent.name:
            item.add_marker(pytest.mark.require_foo)
        if 'bar' in item.parent.name:
            item.add_marker(pytest.mark.require_bar)

I would love to factor this method to live in a utilities.py but I have no idea how to unit test this? The simplest thing would be to in-place create a list [pytest.Item, pytest.Item] which are some hand-crafted test objects. However, that's not super-easy to do, I get the following error message

Direct construction of Item has been deprecated, please use Item.from_parent.

Any tips on how to unit test this code? I could created baroque mocks but would prefer not to...

[nicoddemus]

Yeah Item is not meant to be instantiated directly.

One aspect that is often overlooked is that you don't need to test actual Item objects, but any object which implements the same interface/protocol.

You can use mock.create_autospec to create a mock object with the same interface.

[jandom]

Thanks @nicoddemus this was very helpful! Posting a useful snippet for anybody else wanting to test their pytest utility code

from conftest_utilities import collection_modifyitems
import pytest
from unittest import mock

def test_collection_modifyitems_invalid():
    mock_parent = mock.create_autospec(pytest.Item)
    mock_parent.name = 'foo'
    mock_item = mock.create_autospec(pytest.Item)
    mock_item.parent = mock_parent
    collection_modifyitems([mock_item])
    assert mock_item.add_marker.call_args[0] == (pytest.mark.require_foo,)