Add a way to easily test units

[mathbunnyru]

Full description is in the issue.
Fix: #1353

[mathbunnyru]

Works locally!

---------------------------------------------------------------------------------------------- live log call -----------------------------------------------------------------------------------------------
2021-06-26 18:54:03 [    INFO] Searching for units tests in /home/asalikhov/docker-stacks/test/../scipy-notebook/test/units (test_units.py:17)
2021-06-26 18:54:03 [    INFO] Running jupyter/scipy-notebook with args {'detach': True, 'ports': {'8888/tcp': 8888}, 'volumes': {'/home/asalikhov/docker-stacks/test/../scipy-notebook/test/units': {'bind': '/home/jovyan/data', 'mode': 'ro'}}, 'tty': True, 'command': ['start.sh', 'bash', '-c', 'sleep infinity']} ... (conftest.py:80)
2021-06-26 18:54:03 [    INFO] Running unit test: unit_pandas.py (test_units.py:31)
PASSED

[mathbunnyru]

This seems to be ready.
Overall, simple tests are just a few lines of python code without any pytest / docker, execute and behave exactly the same as before, more readable.
And actually before adding README.md, the number of lines of code reduced, which is also great.

[consideRatio]

@mathbunnyru can you help me help you get this reviewed by applying the autoformatting as a dedicated PR?

For me, the main point of having autoformatters is to avoid ending up with PRs including formatting changes alongside logic changes to help the review process and avoid cluttering git history when git blame is used. I suggest we do pre-commit run --all.

Oh... I tried that and conclude we don't have autoformatting regarding trailing commas or similar. I would suggest we use black as an autoformatter if you want to have it be consistent about such style matters and then we do pre-commit run black --all once in a dedicated PR.

UPDATE: I created #1387

[mathbunnyru]

@mathbunnyru can you help me help you get this reviewed by applying the autoformatting as a dedicated PR?

These were not automatic changes.
I only made changes in test files because I was looking at them and making them consistent.

[mathbunnyru]

@consideRatio you asked to make it easier for you to review these changes.
No problem :)

I made a separate PR, which changes the style in the test files.
#1388
I'm going to merge this as soon as it passes the tests.

Then I'm going to merge master to the branch in this PR and this change will be purely adding unit tests.

In parallel, I'll ask you to merge master in your branch and rerun black.
The reason for this is simple - I've actually given some time to make the code in this repo look good.
And I think manually formatted code + flake8 behaves better than black does.
I will find some examples of such behavior.
Sorry, I think black is great, when the code was not good in the beginning.
But if it already is, then it can do some things, which are not pretty.

[mathbunnyru]

@consideRatio now this is purely feature add.

[mathbunnyru]

@consideRatio now it's your turn to review 😆

[consideRatio]

I've made one suggestion that I think can make this code more robust in case we want to publish to someplace else than dockerhub such as quay.io, but other than that i think this looks amazing! Nice work!

[consideRatio]

LGTM!