chore: replace TestCase with pytest

[gretelliz]

Closes #88

Summary

Replaced TestCase with pytest test suite or test case

Local Tests

Not needed

End-to-End Tests

Not needed

[viniarck]

@gretelliz, it's a good start. But notice, there was a regression of 30% in terms of unit test coverage. In the warning messages it's pointing out a conflict with __init__ being called on TestStruct.

tests/unit/v0x01/test_asynchronous/test_flow_removed.py:8
  /home/scrutinizer/build/tests/unit/v0x01/test_asynchronous/test_flow_removed.py:8: PytestCollectionWarning: cannot collect test class 'TestFlowRemoved' because it has a __init__ constructor (from: tests/unit/v0x01/test_asynchronous/test_flow_removed.py)
    class TestFlowRemoved(TestStruct):

A lot of Test Suites were inherinting from TestStruct, but since pytest won't allow __init__ to be overwritten this will need to be refactored to be compatible. If you take a look on TestStruct, essentially it's just providing convenience to set a particular struct object and then run a few common tests.

I believe the path with least resistance here would to refactor TestStruct as StructTest, and then on each test suite that used to be a sub class from TestStruct, you no longer subclass it, but then just define a test_base or whatever and then reuse all the current setters and then you call run_tests() - which would be a new method on TestStruct that would call every expected base test_* methods on StructTest, essentially we'd be losing part of the automatic test collection that we used to have with the inheritance but I believe it's a decent compromise considering this refactor, here's an example:

class TestHello:
    """Hello message tests (also those in :class:`.TestDump`)."""

    def test_base(self):
        """Configure raw file and its object in parent class (TestDump)."""
        struct_test = StructTest()
        struct_test.set_raw_dump_file('v0x04', 'ofpt_hello')
        struct_test.set_raw_dump_object(Hello, xid=62,
                                        elements=_new_list_of_elements())
        struct_test.set_minimum_size(8)
        struct_test.run_tests()

The pytest way is typically with fixtures to do this sort of thing, but from what I'm initially seeing here it would be much harder to do. Let me know if you're seeing something simpler.

[viniarck]

I'll convert this to draft since there has been no updates on this PR.

[viniarck]

Closing this PR in favor of #90