Test failure on big-endian systems

[hosiet]

With the rebuild of fscacher on Debian Unstable/Sid ( https://tracker.debian.org/pkg/fscacher ), the following test error via Debian autopkgtest is found on s390x architecture:

 45s autopkgtest [03:10:08]: test pybuild-autopkgtest: [-----------------------
 46s pybuild-autopkgtest
 46s I: pybuild base:311: cd /tmp/autopkgtest-lxc.w959byms/downtmp/autopkgtest_tmp/build; python3.12 -m pytest 
 47s ============================= test session starts ==============================
 47s platform linux -- Python 3.12.7, pytest-8.3.3, pluggy-1.5.0
 47s rootdir: /tmp/autopkgtest-lxc.w959byms/downtmp/autopkgtest_tmp/build
 47s plugins: typeguard-4.4.1, cov-5.0.0, mock-3.14.0, rerunfailures-14.0
 47s collected 27 items
 47s 
 47s tests/test_cache.py ................s.....                               [ 81%]
 47s tests/test_util.py ...F.                                                 [100%]
 47s 
 47s =================================== FAILURES ===================================
 47s _______________________ test_xor_bytes[\x12\xab-4-&\xab] _______________________
 47s 
 47s b1 = b'\x12\xab', b2 = b'4', r = b'&\xab'
 47s 
 47s     @pytest.mark.parametrize(
 47s         "b1,b2,r",
 47s         [
 47s             (b"\x12", b"\x34", b"\x26"),
 47s             (b"\0\x12", b"\0\x34", b"\0\x26"),
 47s             (b"\x12\0", b"\x34\0", b"\x26\0"),
 47s             (b"\x12\xAB", b"\x34", b"\x26\xAB"),
 47s             (b"\x12\xAB", b"\x34\xCD", b"\x26\x66"),
 47s         ],
 47s     )
 47s     def test_xor_bytes(b1: bytes, b2: bytes, r: bytes) -> None:
 47s >       assert xor_bytes(b1, b2) == r
 47s E       AssertionError: assert b'\x12\x9f' == b'&\xab'
 47s E         
 47s E         At index 0 diff: b'\x12' != b'&'
 47s E         Use -v to get more diff
 47s 
 47s tests/test_util.py:16: AssertionError
 47s =========================== short test summary info ============================
 47s FAILED tests/test_util.py::test_xor_bytes[\x12\xab-4-&\xab] - AssertionError:...
 47s =================== 1 failed, 25 passed, 1 skipped in 0.59s ====================
 47s E: pybuild pybuild:389: test: plugin pyproject failed with: exit code=1: cd /tmp/autopkgtest-lxc.w959byms/downtmp/autopkgtest_tmp/build; python3.12 -m pytest 
 47s pybuild-autopkgtest: error: pybuild --autopkgtest --test-pytest -i python{version} -p 3.12 returned exit code 13
 47s make: *** [/tmp/LMVqFCDGDw/run:4: pybuild-autopkgtest] Error 25
 47s pybuild-autopkgtest: error: /tmp/LMVqFCDGDw/run pybuild-autopkgtest returned exit code 2
 47s autopkgtest [03:10:10]: test pybuild-autopkgtest: -----------------------]

To my understanding, it should be the xor_byte() function implicitly assuming the little-endian hardware architecture.

The raw test log can be found at https://ci.debian.net/packages/f/fscacher/testing/s390x/54726807/ .

Please let me know how you would like to have this issue fixed, such as skipping the test on big-endians or pushing an actual fix. Thanks!

[hosiet]

Ping. Any updates on this one? I am not sure whether the current implementation of xor_bytes() is working as intended. If yes, we should be able to safely skip this test on big-endian systems.

[yarikoptic]

Thank you @hosiet for the report and sorry for the delay. Hopefully

• BF: force "little" endianness while xor_byte #102

would address it. I tested on zelenka -- that test passes with the patch.