ci: Fail CI if xfails pass unexpectedly

[romanc]

Description

Be strict about tests marked with xfail. If they pass unexpectedly, fail the testsuite instead of logging an XPASS.

Requirements

• All fixes and/or new features come with corresponding tests.
• Important design decisions have been documented in the appropriate ADR inside the docs/development/ADRs/ folder.
  N/A

[romanc]

@tehrengruber it looks like

gt4py/tests/next_tests/integration_tests/feature_tests/ffront_tests/test_execution.py

Lines 264 to 277 in 3249aa5

	@pytest.mark.uses_tuple_args
	@pytest.mark.xfail(
	reason="Not implemented in frontend (implicit size arg handling needs to be adopted) and GTIR embedded backend."
	)
	def test_tuple_arg_with_different_but_promotable_dims(cartesian_case):
	@gtx.field_operator
	def testee(a: tuple[cases.IField, cases.IJField]) -> cases.IJField:
	return a[0] + 2 * a[1]
	cases.verify_with_default_data(
	cartesian_case,
	testee,
	ref=lambda a: a[0][:, np.newaxis] + 2 * a[1],
	)

passes with the numpy backend despite the general xfail. We could add strict=False to this test case. What do you think?

[egparedes]

LGTM

[egparedes]

Debugging leftover?

[romanc]

Nice! Thanks for fixing this 🚀