convert test dirs to packages

[wholmgren]

• Closes #xxxx
• I am familiar with the contributing guidelines
• Tests added
• Updates entries to docs/sphinx/source/api.rst for API changes.
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels and Milestone are assigned to the Pull Request and linked Issue.

@mikofski and I have been trying to figure out why vscode doesn't discover pvlib's test suite in microsoft/vscode-python#15398

This PR:

• adds __init__.py files to the test directories
• changes imports of test helpers (e.g. DATA_DIR) to use relative imports

Current pytest documentation says that you should not import from conftest.py unless you are using packages, so this PR brings us into alignment with that directive. My memory is that pytest used to discourage __init__.py in test directories, but maybe I misunderstood or I am misremembering the whole thing. The documentation example for including tests within the package (i.e. pvlib/tests rather than src/pvlib, tests) shows including an __init__.py file within the test directory.

@mikofski does this also fix the problem for you? You might need to pip uninstall pvlib; pip install -e . and you might need to reload vscode - I didn't carefully track what was important as I banged away on my keyboard.

[mikofski]

Yes! Success! vscode is working again! No changes required, just checking out your branch seems to have fixed it. I have vanilla vscode settings:

{
    "python.testing.pytestArgs": [],
    "python.testing.unittestEnabled": false,
    "python.testing.nosetestsEnabled": false,
    "python.testing.pytestEnabled": true,
    "python.pythonPath": "venv\\Scripts\\python.exe"
}

based on a pip editable install into a virtual environment.

Nope, I didn't have to reinstall or change anything. Thanks so much for figuring this out. I thought I had run through all these options, and Brett Cannon couldn't figure it out either. I really appreciate the time you put into this.

[mikofski]

lgtm, all vscode tests passing, everything looks good, thanks for moving location/solpos tests up to conftests and for cleaning up imports.

[mikofski]

My memory is that pytest used to discourage __init__.py in test directories

I remember reading that too, I dunno what the logic was, but seems like since we're using conftest.py better for tests to be a subpackage, and doesn't hurt.

everything looks good to me, does anyone object if I merge it?

[wholmgren]

Probably worth a whats new note. incoming...

[mikofski]

closed microsoft/vscode-python#15398

[cwhanse]

Packages and subpackages are somewhat mysterious to me, so I can't comment on using or not using them. +1 to moving those few fixtures into conftest.py

[kandersolar]

Ok with me. Maybe I should be using vscode too!

[kandersolar]

I wish pytest could parametrize across fixtures directly instead of having to do this sort of tapdance. FYI in cases with more than one fixture lookup like this, using request and request.getfixturevalue(request.param) can be handy: https://stackoverflow.com/a/42599627

[wholmgren]

thanks I didn't know about that!