test: botfactory, UserFactory, and IRCFactory

[Exirel]

I wanted more from Sopel's test tools, for 2 reasons:

• increase the test coverage for the bot, its internals and its plugins
• help plugin authors to test their plugins

My approach in this PR is the following:

• sopel.tests.mocks contains mocks: they generate fake IRC lines (User and IRC Server) or pretend to be a backend of some sort (IRC Connection Backend)
• sopel.tests.factories contains factories: they are helper classes, they help to create mock objects with different parameters. Each factory implements a __call__ method, so they act as callable, like this: mock_bot = botfactory(...)
• sopel.tests.pytest_plugin: it's a plugin for pytest, that will be automatically loaded by pytest thanks to entry point. It will bring shared fixture for everyone to use, mostly generating pre-made factories

[dgw]

Aside from notes in the docstrings, I'm not sure we want to start calling things "Factory". I know you're not set on the naming yet; just weighing in! Personally, I would write everything as MockSomething, and have them all be classes (including botfactory) for consistency, but that's just one idea.

[Exirel]

Ok, now I think the interface works well enough. The next step is to squash the commits.

To move forward with tests and their tools, I'll need #1732 to be merged with that PR, so I will be able to run a command, join the command thread, then check the bot's output.

@dgw awaiting your approval to rebase/squash. :)

[Exirel]

@dgw after so many changes in master (about ~100 commits of differences) I had to rebase, so I also squashed the previous commits. I know it's a big chunk of code to review. The good news is that it doesn't change the core of Sopel, and affect only the tests. Now with #1732 I should be able to write more complex tests, that will verify that the bot works from its dispatch method to the last bit of coretasks.

Which is pretty nice in my opinion and opens a ton of possibilities for the future. 🕺

[Exirel]

So for some reason I removed the import re in the wrong commit, so my squash didn't result as intended. Now it's fixed properly, I won't get caught in that again!

[Exirel]

Yet another "sopel/modules/search.py::test_example_duck_1 FAILED". Go to hell, DDG.

[dgw]

Go to hell, DDG.

Big mood. 😂

[dgw]

Phew! Surprisingly, I got through this in just over half an hour.

Have your daily (?) dose of typo fixes, a healthy helping of consistency tweaks, and a couple honest questions for dessert. I really like how much this simplifies the tests, even if the diff doesn't look like it (net +419 lines overall, but the actual unit test files are net negative).

[Exirel]

@dgw I didn't rebase/squash, you shouldn't have trouble with the new review.

I think this is in a good shape - good enough for a release - but I certainly can't wait for all the feedbacks that will help improve and build on what's in here.

Kind of excited for the future right now! 🎉

[Exirel]

Coverage increased (+1.3%) to 52.652%

Me: 💥 👶

[dgw]

I'm approving this despite a couple little formatting things, which you will probably handle during squash. If they aren't taken care of now, they'll be handled later by flake8 checks I plan to add after 7.0.

[Exirel]

💥 👶 😎