Unittest: ignore test cases that are also ABC

Ideas
15

I’m curious if anyone has a reason why we shouldn’t change unittest to understand abc classes? Currently this example fails:

import abc
import unittest

class Mixin(unittest.TestCase, abc.ABC):
    @abc.abstractmethod
    def make_backend(self):
        ...

    def test_it(self):
        assert 1 == 2

unittest tries to instantiate the TestCase class, which it cannot do:

... etc ...
  File "/usr/local/pyenv/pyenv/versions/3.12.4/lib/python3.12/unittest/suite.py", line 24, in __init__
    self.addTests(tests)
  File "/usr/local/pyenv/pyenv/versions/3.12.4/lib/python3.12/unittest/suite.py", line 57, in addTests
    for test in tests:
TypeError: Can't instantiate abstract class Mixin without an implementation for abstract method 'make_backend'

Since the code as presented is now an error, wouldn’t it be better to update unittest to not attempt to instantiate classes that can’t be instantiated?

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