Full migration to idiomatic pytest

[Lotram]

Last PR to close #1160

This PR mostly does 2 things:

1. migrate everything to more standard pytest (fixtures, parametrize...)
2. Improve consistency across service test files.

Standard Pytest

This change is quite opinionated, but here is why I think it improves the code:

• Remove a lot of silent mutations. The tests used to rely on manual copies, setting / unsetting environment variable etc to make everything works. Tests are now isolated by construction. We use standard fixture for tmp paths, env variable overrides, and we define our own to create services, issues etc.
• composition over inheritance. Standard principle too, we used to rely a lot on test class inheritance, which is quite fragile, and prevented us to easily modify tests (hence this big PR)
• warnings are now considered as errors, so we can detect and fix them (except for taskw deprecation warnings, as we can't really do anything about that for now). Several bugs were detected and fixed thanks to that.

Service tests consistency

Each service test was defining and using its data differently, once again making it harder to add a change for all services at once, I tried to make them a bit more similar. I added a few tests to ensure basic consistency

I tried to create atomic commits to ease the review. If that's still too much, I can create multiple PRs

[ryneeverett]

• FYI, I'm thinking I'll squash merge this one. The commit structure was helpful for review but I'm not sure how helpful it would be in a git blame scenario. I also noticed that the commits do not appear to all be atomic in the sense that the tests pass -- f825c0c removes ConfigTest which is still depended on.
• Please update the tutorial.rst Tests section to reflect the new pattern.
• This is more an idea for the future than something I'd want added to this PR, but would is make sense to make config a shared fixture across services? My thought is that is might be confusing that the default differs from SERVICE_CONFIG. It would require some reworking in a lot of the services, but it seems nice if they all used a fixture like Trello:

    @pytest.fixture
    def config(self):
        return {'general': {'targets': ['myservice']}, 'myservice': {**SERVICE_CONFIG}}

[Lotram]

FYI, I'm thinking I'll squash merge this one. The commit structure was helpful for review but I'm not sure how helpful it would be in a git blame scenario. I also noticed that the commits do not appear to all be atomic in the sense that the tests pass -- f825c0c removes ConfigTest which is still depended on.

Agreed, I created multiple commits to avoid having a single really big diff, but we can definitely squash them before merging. Do you want me to do it now, or wait ?

Please update the tutorial.rst Tests section to reflect the new pattern.
Sure

This is more an idea for the future than something I'd want added to this PR, but would is make sense to make config a shared fixture across services? My thought is that is might be confusing that the default differs from SERVICE_CONFIG. It would require some reworking in a lot of the services, but it seems nice if they all used a fixture like Trello

Not sure I understand how you want to pass the SERVICE_CONFIG dict to a shared fixture. Through a factory maybe ? Something like:

@pytest.fixture
def config_factory(service_config):
    def _config():
        return {'general': {'targets': ['myservice']}, 'myservice': {**service_config}}
    return _config

# in test_github.py
SERVICE_CONFIG = {}
@pytest.fixture
def config():
    return config_factory(SERVICE_CONFIG)

[Lotram]

@ryneeverett I added a commit to speed up the documentation tests (as well as the actual doc generation).

[ryneeverett]

I'll squash at the end since the github UI makes it super easy, I just wanted to get your opinion. I hadn't been squashing your PR's lately since the commits have been well-structured and truly atomic.

Not sure I understand how you want to pass the SERVICE_CONFIG dict to a shared fixture.

It seems like we could use the request fixture and do something like:

    @pytest.fixture
    def config(self, request):
        return {'general': {'targets': ['myservice']}, 'myservice': {**request.module.SERVICE_CONFIG}}