[cppyy] Review xfail'ed tests

[guitargeek]

All xfail'ed cppyy tests have been reviewed, and the ones that are
actually failing are now marked as xfail(strict=True), so the test
fails if it unexpectedly passes.

This gives us a very useful baseline for what works now in ROOT and what
doesn't, and we'll learn when our developments like the cppyy upgrade on
the CppInterOp-based version will fix some tests.

There are some tests remaining that can't be run because they crash, and
therefore the strict mode doesn't make sense there. But the number of
these tests is not high, and now we always give a reason for why they
crash:

git grep xfail | grep -v "strict"

test_concurrent.py:    @mark.xfail(run=False, reason="Crashes because TClingCallFunc generates wrong code")
test_concurrent.py:    @mark.xfail(run=False, reason="Crashes because the interpreter emits too many warnings")
test_concurrent.py:    @mark.xfail(run=False, reason="segmentation violation")
test_cpp11features.py:    @mark.xfail(run=False, reason = "Crashes")
test_datatypes.py:    @mark.xfail(run=False, reason="segmentation violation")
test_datatypes.py:    @mark.xfail(run=False, reason="error code: Subprocess aborted")
test_doc_features.py:    @mark.xfail(run=False, condition=WINDOWS_BITS == 64, reason = "Crashes on Windows 64 bit")
test_fragile.py:    @mark.xfail(run=False, condition=has_asserts(),
test_fragile.py:    @mark.xfail(run=False, reason="Fatal Python error: Aborted")
test_fragile.py:    @mark.xfail(run=False, reason="Fatal Python error: Aborted")
test_fragile.py:    @mark.xfail(run=False, condition=is_modules_off(), reason="Crashes on build with modules off: Fatal Python error: Segmentation fault")
test_lowlevel.py:    @mark.xfail(run=False, condition=IS_WINDOWS, reason="Windows fatal exception: access violation")
test_regression.py:    @mark.xfail(run=WINDOWS_BITS != 64, condition=IS_MAC_ARM | WINDOWS_BITS == 64, reason = "Crashes on Windows 64 bit and fails macOS ARM with" \
test_stltypes.py:    @mark.xfail(run=False, reason="Fatal Python error: Segmentation fault")
test_stltypes.py:    @mark.xfail(run=False, condition=WINDOWS_BITS == 64, reason="Crashes on Windows 64 bit")
test_templates.py:    @mark.xfail(run=False, reason="error code: Subprocess aborted")

A future development could be to ensure in Cling or cppyy that these
tests at least don't crash but fail gracefully, but that's better to be
done after the cppyy upgrade because some tests might be fixed anyway.

Some tests remain skipped for good reasons:

git grep "mark\.skip"

test_boost.py:@mark.skipif(noboost == True, reason="boost not found")
test_boost.py:@mark.skipif(noboost == True, reason="boost not found")
test_boost.py:@mark.skipif(noboost == True, reason="boost not found")
test_boost.py:@mark.skipif(noboost == True, reason="boost not found")
test_boost.py:    @mark.skipif(noboost, reason="boost not found")
test_eigen.py:@mark.skipif(eigen_path is None, reason="Eigen not found")
test_eigen.py:@mark.skipif(eigen_path is None, reason="Eigen not found")
test_fragile.py:    @mark.skip(reason="This test is very verbose since it sets gDebug to True")
test_fragile.py:    @mark.skip(reason="Not actually a cppyy test")
test_fragile.py:    @mark.skipif(not has_cpp_20(), reason="std::span requires C++20")
test_leakcheck.py:@mark.skipif(nopsutil == True, reason="module psutil not installed")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_leakcheck.py:    @mark.skip(reason="disabled due to its sporadic nature, especially fragile on VMs")
test_numba.py:@mark.skipif(has_numba == False, reason="numba not found")
test_numba.py:    @mark.skip(reason="Numba tests comparing execution times are sensitive and fail sporadically")
test_numba.py:    @mark.skip(reason="Numba tests comparing execution times are sensitive and fail sporadically.")
test_numba.py:    @mark.skip(reason="Numba tests comparing execution times are sensitive and fail sporadically.")
test_numba.py:    @mark.skip(reason="Numba tests comparing execution times are sensitive and fail sporadically.")
test_numba.py:@mark.skipif(has_numba == False, reason="numba not found")
test_eigen.py:    @mark.skipif(eigen_path is None, reason="Eigen not found")
test_pythonify.py:    @mark.skip(reason="Garbage collection tests are fragile")
test_regression.py:    @mark.skip(reason="For ROOT, we don't enable AVX by default ('-mavx' is not passed to Cling)")
test_stltypes.py:@mark.skipif(not has_cpp_20(), reason="std::span requires C++20")

Sorry that these git grep commands don't show the names of the tests!
They are to illustrate how many tests are still marked as skip/xfail
without strict=True.

Closes #20085.

[github-actions]

Test Results

    22 files      22 suites   3d 11h 21m 54s ⏱️
 3 812 tests  3 812 ✅ 0 💤 0 ❌
76 684 runs  76 684 ✅ 0 💤 0 ❌

Results for commit ae95b68.

♻️ This comment has been updated with latest results.