Add pytest for unit testing

[JCZuurmond]

This PR adds pytest for unit testing.

I tried to follow the dbt setup as much as possible. They have a unit test folder with unit tests. I followed the pytest best practice to mimick the package structure as well.

It is a little awkward since SQL tests and python tests are combined. The set-up expects the usually pytest directory structure in the test/unit folder - while the convention is to put those in the tests/ folder.

[mikaelene]

We had a discussion about testing the different ways for connection. Is this to support that? I guess that we need to clarify what is what with regards to the dbt package tests. Have the other adaptors anything like this?

[JCZuurmond]

yes, this indeed is intended for testing the different ways for connection. I want to use it for #100. And more generally it can be used for testing the python code.

dbt and dbt-spark have such a test/unit folder for python testing. I added subfolders to organize the test in the usual pytest way.

@swanderz : Could you have a look to see if the CI will run the python unit tests.

[dataders]

@JCZuurmond looking like we're in the same boat as before w.r.t getting CI working from your fork. i just changed some settings, can you try pushing a new commit to see if my tweaks fixed things?

[JCZuurmond]

the CI ran, the checks only show integration-sqlserver

[JCZuurmond]

CI passes!

[dataders]

@JCZuurmond this PR is much appreciated. I'm certainly a python testing and packaging newbie, so help in this area is great. I had originally assumed that the test/unit/ dir of dbt-spark was for testing the Python classes and functions, but it looks as if there's some integration testing in there as well?

I think we're lucky that with the connection-sqlserver and connection-azuresql CircleCI jobs, we cover most of the of the connection profile differences without having to roll our own pytest suite. My original thought is that this PR would serve so we could write unit tests for the python functions you've added, namely:

• convert_bytes_to_mswindows_byte_string
• convert_access_token_to_mswindows_byte_string
• get_cli_access_token, and
• get_sp_access_token.

But I'm unsure how the last two could be unit tests without also being integration tests... 🤷
That said this PR is all about setting the stage for future unit tests.

I want to use it for #100. And more generally it can be used for testing the python code.

as for this... I have no idea why there is only one check running instead of four.

the CI ran, the checks only show integration-sqlserver

a few asks -- can you add:

1. pull from master and add a changelog entry?
2. code formatting check for black @mikaelene's partial to it over flake8

[JCZuurmond]

@swanderz : I can shoot in a first PR to for the unit tests. I was thinking to do some mocking to test the azure login methods.

1. I have added a changelog entry
2. I would do that in a different PR. Maybe recommendation would be to go for WIP: Python conventions #73 and use pre-commit. But seeing that dbt does not use pre-commit, I am ok with not usin it.

This PR is ok to be merged in my opinion!

[dataders]

as for this... I have no idea why there is only one check running instead of four.

the CI ran, the checks only show integration-sqlserver

So deleted a blank line and now all the jobs run...

More importantly, everything is passing now! LGTM