fix(tests): match blocks by qindices in apply() pybind test helper

[yingjerkao]

Summary

Fixes the two pre-existing failures in tests/test_apply_pybind.py:

• TestApplyBlockFermionicUniTensor::test_apply_applies_signflips
• TestApplyBlockFermionicUniTensor::test_apply_inplace_applies_signflips

The backend is correct — the test helper was the bug. T.apply() output was verified element-wise against the hand-built BFUT3PERM reference over the full tensor shape: 0 mismatches, including the expected sign-flipped entries (−5, −6, −7, −8), matching the C++ LinAlgElementwise expectation in tests/BlockFermionicUniTensor_test.cpp.

Root cause

_are_nearly_eq zipped get_blocks_() by list position, but block order is not canonical: permute().contiguous() keeps the source tensor's block enumeration order, while a freshly constructed reference tensor enumerates blocks in canonical qnum order. Positional pairing therefore compared unrelated blocks. The C++ helper AreNearlyEqUniTensor (tests/test_tools.cpp) explicitly matches blocks by quantum numbers ("they might be not in the same order!"), which is why the C++ test passes.

Changes

• Rewrite _are_nearly_eq to match blocks by get_qindices() and require signflip() flags to agree before comparing raw block data. Deliberately no sign-folding, so the tests stay sensitive to whether apply() actually baked the pending signs in (verified: unapplied T vs reference → False, applied → True).
• Use the public Bond.redirect_() instead of the c_redirect_ shadow binding (equivalent on master via the Bond_conti.py glue wrapper; avoids a conflict with the in-progress shadow-API removal branch).

Test plan

• tests/test_apply_pybind.py: 9 passed (was 7 passed / 2 failed)
• Full pytests/ suite: 28 passed (matches baseline)
• Test-only change; no C++ touched

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request updates the _are_nearly_eq helper function in tests/test_apply_pybind.py to match block UniTensors by their quantum-number indices instead of their positions, and to verify that pending signflips agree. Additionally, it replaces the call to c_redirect_() with redirect_() in _make_bfut3(). There are no review comments, so no further feedback is provided.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.73%. Comparing base (33f5c23) to head (52091dc).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #985      +/-   ##
==========================================
+ Coverage   57.71%   57.73%   +0.02%     
==========================================
  Files         229      229              
  Lines       33468    33468              
  Branches       71       71              
==========================================
+ Hits        19315    19322       +7     
+ Misses      14132    14124       -8     
- Partials       21       22       +1     

Flag	Coverage Δ
cpp	57.66% <ø> (+0.01%)	⬆️
python	63.61% <ø> (+0.26%)	⬆️

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Components	Coverage Δ
C++ backend	55.48% <ø> (+0.01%)	⬆️
Python bindings	72.05% <ø> (+0.06%)	⬆️
Python package	63.61% <ø> (+0.26%)	⬆️
see 4 files with indirect coverage changes

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[pcchen]

Code Review

Rewrites _are_nearly_eq in tests/test_apply_pybind.py to match blocks by quantum-number sector (get_qindices) instead of list position, requiring signflip() agreement before comparing block data; plus c_redirect_ → redirect_.

Correct as far as it goes

• The _are_nearly_eq sector-matching + signflip-agreement logic is right — it matches the C++ AreNearlyEqUniTensor (blocks are not in canonical order between permute().contiguous() and a freshly-built reference), and deliberately doesn't sign-fold, so it stays sensitive to whether apply() actually baked the pending signs in. ✅
• redirect_() is correct on current master (post-refactor(pybind): bind in-place methods directly, drop the c__* shadow API #986, which binds it directly). ✅

🟠 Finding 1 — the fix isn't actually enforced by CI

CI runs pytest pytests/ (ci-cmake_tests.yml:140), and this file lives under tests/, which pytest does not discover there. So tests/test_apply_pybind.py has never been run by CI — that's why the "2 failures" only appear in manual runs, and why #985's green checks don't include them. This PR fixes the helper but leaves the file where CI won't run it, so the now-passing tests remain silently skipped. To make it a real fix, also git mv tests/test_apply_pybind.py pytests/apply_test.py so CI enforces it.

🟠 Finding 2 — duplicates #1001

#1001 (still open, CONFLICTING) does the identical _are_nearly_eq rewrite and the pytests/ file move and the redirect_ change, as part of its larger Bond-immutable work. #985 and #1001 modify the same lines, so they'll conflict — whichever merges second must drop this. Given #1001 is currently stuck (changes-requested + conflicts + gateway-narrowing follow-up), landing #985 — made complete by adding the file move — is a pragmatic way to fix these tests now, after which #1001 drops its copy.

Recommendation

Good, correct fix — but please add the pytests/ relocation (otherwise it's a no-op in CI), and coordinate with #1001 so the duplicate _are_nearly_eq change doesn't collide.

Posted by Claude Code on behalf of @pcchen

[yingjerkao]

Addressed the review findings:

Finding 1 (fix not enforced by CI) — resolved. Moved tests/test_apply_pybind.py → pytests/apply_test.py (commit 52091dc, a 100% rename) so CI's pytest pytests/ discovers and runs it. The branch was also brought up to date with master (168 commits behind → current) so the relocation is verified against today's code, not a stale tree:

• pytests/apply_test.py → 9 passed (both previously-failing signflip tests included)
• full pytests/ → 135 passed, 1 skipped — no collection breakage

Finding 2 (duplicates #1001) — acknowledged. #1001 is still OPEN / CONFLICTING / DIRTY, so landing #985 (now made complete by the file move) remains the pragmatic way to fix these tests. Once #985 merges, #1001 should drop its duplicate _are_nearly_eq rewrite + pytests/ move to avoid the collision.

Posted by Claude Code on behalf of @pcchen