Transition testing framework to pytest

[jadchaar]

Pull Request Checklist

Thank you for taking the time to improve Arrow! Before submitting your pull request, please check all appropriate boxes:

• 🧪 Added tests for changed code.
• 🛠️ All tests pass when run locally (run tox or make test to find out!).
• 📚 Updated documentation for changed code.
• ⏩ Code is up-to-date with the master branch.

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Description of Changes

Closes: #594

This is the first iteration of the transition to Pytest. We should ultimately move away from the x-unit style of setUp() functions to native Pytest fixtures, but this will do for now.

[codecov-io]

Codecov Report

Merging #751 into master will not change coverage.
The diff coverage is n/a.

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##           master   #751   +/-   ##
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  Coverage     100%   100%           
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  Files           9      9           
  Lines        1669   1669           
  Branches      282    282           
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  Hits         1669   1669

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[systemcatch]

Hey @jadchaar solid PR, pytest looks so much better than Chai. I've taken a quick look over and just have one initial comment, I'll review in depth later on.

[systemcatch]

Hey @jadchaar I was able to successfully clone your branch and run the new tests, everything passed fine.

[jadchaar]

Fantastic. I have locked the dependency versions like you requested.

[systemcatch]

Looks like the last version of pytest to support 2.7 is 4.6 (https://docs.pytest.org/en/latest/py27-py34-deprecation.html). 😞

[jadchaar]

@systemcatch I pushed a fix for this in the latest commit.

[systemcatch]

All good on my end Jad, I'll leave merging to you in case there's anything extra you want to add.

[jadchaar]

I don't have anything to add :). I'll go ahead and merge this.