test: project scope fixtures for repo root and data dir

[aaraney]

This is a proof of concept solution to #570. For this to work, this will require running tests with pytest. In short, this exposes the repo root and data directory paths as pytest fixtures that can be utilized by pytest style tests and unittest.UnitTest tests. The unittest fixture variants set private properties on unittest.UnitTest instances.

Example of adding this functionality to a unittest.UnitTest:

import unittest
import pytest

@pytest.mark.usefixtures("repo_root_unittest")
class TestFoo(unittest.TestCase):
    def test_foo(self):
        # do something with repo root
        (self._repo_root / "LICENSE").read_text()

For those who have not been indoctrinated, here are a few links that will be helpful to understand pytests integration with unittest, the concept of a fixture, and fixture scopes.

• https://docs.pytest.org/en/7.1.x/how-to/unittest.html
• https://docs.pytest.org/en/7.1.x/explanation/fixtures.html#about-fixtures
• https://docs.pytest.org/en/7.1.x/reference/fixtures.html#higher-scoped-fixtures-are-executed-first

edit: fixed link to the description / diagram of fixture scopes

[aaraney]

reworded the commit.

[christophertubbs]

Any chance you can make a semi-bs/unnecessary fixture and refactor a low stakes unit test implementation to use it for a more concrete example? Or I guess add a new unit test that tests something super small as a rough example for those not in the know and don't know what 'read the manual' means?

[aaraney]

@christophertubbs, for sure! See this https://github.com/NOAA-OWP/DMOD/pull/572/files#diff-89ecca2cc7163ef202e63ea12a25ca8dea5d17dae557d840608dd61128c739e2

[christophertubbs]

I absolutely love it. I'd go ahead and merge it if the unit test didn't whine about not knowing what pytest was. Maybe that needs to work itself into the requirements.txt or something.