Incorrect instantiation of incomplete ABC subclass in test_collections::validate_abstract_methods`

[guilhermeleobas]

Bug report

Bug description:

The test for missing abstract methods in validate_abstract_methods incorrectly attempted to instantiate the generated class C with an argument (C(name)), which always raises a TypeError: C() takes no arguments. Although the test originally passes, it passes for the wrong reason.

cpython/Lib/test/test_collections.py

Lines 727 to 739 in 481d5b5

	def validate_abstract_methods(self, abc, *names):
	methodstubs = dict.fromkeys(names, lambda s, *args: 0)
	# everything should work will all required methods are present
	C = type('C', (abc,), methodstubs)
	C()
	# instantiation should fail if a required method is missing
	for name in names:
	stubs = methodstubs.copy()
	del stubs[name]
	C = type('C', (abc,), stubs)
	self.assertRaises(TypeError, C, name)

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-137463: Update validate_abstract_methods in test_collections.py #137464
• [3.14] gh-137463: Update validate_abstract_methods in test_collections.py (GH-137464) #137503
• [3.13] gh-137463: Update validate_abstract_methods in test_collections.py (GH-137464) #137516
• [3.13] gh-137463: Update validate_abstract_methods in test_collections.py (GH-137464) #137521