Refactor tests to use pytest fixtures

[Zsailer]

At the last jupyter_server meeting, I mentioned that Jupyter Server's testing framework needs some attention. It's fairly brittle and hasn't been reviewed since we forked from jupyter/notebook.

I argued that we should refactor the tests into pytest's fixture based style. I believe this is more readable and accessible to contributors.

I think it's critical that we get our tests in place ASAP, so that development can move forward confidently. I'm going to spend some time this week refactoring tests.

[Zsailer]

Sharing an update here.

I have a separate repo with pytests for Jupyter Server. Feel free to tour that repo while I continue working.

These tests rely on pytest-tornado and pytest-asyncio. Getting these two libraries to work together took me more time than I'd like to admit... but I think the result is fantastic.

• Tests are explicit.
• They use the async/await syntax.
• The fixtures are straightforward.

The outcome is that tests should be easier to contribute to. I'll add a bit more documentation before moving the test modules over here.

I've also been using Github actions for deploying tests. I love it. I think we should consider moving our tests to Github actions from travis + appveyor. Thoughts?

[maartenbreddels]

Getting these two libraries to work together took me more time than I'd like to admit...

I am not surprised, it's a tricky business, but very important work to get readable tests!

but I think the result is fantastic.

🎉

I think we should consider moving our tests to Github actions from travis + appveyor. Thoughts?

What I've seen, it's pretty fast, so I'm all for it!

Thanks for spearheading this.

[Zsailer]

This is finally finished in #152 and #156!