All tests in `test_bigmem.py` are skipped if `_testcapi` is not available

[ShaharNaveh]

Bug report

Bug description:

This line:

cpython/Lib/test/test_bigmem.py

Line 13 in a00464b

_testcapi = import_helper.import_module('_testcapi')

causes the entire test module to be skipped if _testcapi isn't available but, the only test requiring it is:

cpython/Lib/test/test_bigmem.py

Lines 1261 to 1279 in a00464b

	class ImmortalityTest(unittest.TestCase):
	@bigmemtest(size=_2G, memuse=pointer_size * 9/8)
	def test_stickiness(self, size):
	"""Check that immortality is "sticky", so that
	once an object is immortal it remains so."""
	if size < _2G:
	# Not enough memory to cause immortality on overflow
	return
	o1 = o2 = o3 = o4 = o5 = o6 = o7 = o8 = object()
	l = [o1] * (size-20)
	self.assertFalse(_testcapi.is_immortal(o1))
	for _ in range(30):
	l.append(l[0])
	self.assertTrue(_testcapi.is_immortal(o1))
	del o2, o3, o4, o5, o6, o7, o8
	self.assertTrue(_testcapi.is_immortal(o1))
	del l
	self.assertTrue(_testcapi.is_immortal(o1))

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-152168: Don't skip test_bigmem if _testcapi is missing #152171
• [3.14] gh-152168: Don't skip test_bigmem if _testcapi is missing (GH-152171) #152199

[StanFromIreland]

Do you want to open a PR?

[ShaharNaveh]

Do you want to open a PR?

Would love to!

[StanFromIreland]

Great, if you have any questions feel free to ask here.