test: pin mask constants by re-derivation, lone-high-bit case, relative src import

[thedavidmeister]

Closes #24
Closes #25
Closes #26

Three test-suite hardening items in one file-clustered PR:

• [test-bare-src-import] [LOW] Test uses a bare src/ import (breaks when consumed as a soldeer dependency) #24: the suite imported src/lib/LibCtPop.sol bare, which breaks when the package is consumed as a soldeer dependency; it now imports relatively.
• [unpinned-masks-shared-constant-blindspot] [LOW] Mask constants have no direct test pin; ctpop/ctpopSlow share M1/M2/M4 #25: every CTPOP_M*/CTPOP_H01 constant is pinned by testMaskConstantsRederived, which rebuilds each mask with an independent loop (altMask) instead of trusting the hex literals; previously a corrupted shared constant had no direct value-level test.
• [no-single-high-bit-test] [INFO] No deterministic lone-high-bit (1<<255) test #26: testCtPopLoneHighBit deterministically pins ctpop(1 << 255) == 1 instead of relying on fuzz to reach the top bit.

Also appends the audit/mutation-test-scans.json scan record for this pass.

QA

• Discriminating tests: testMaskConstantsRederived (exact-value assertion per constant, loop-derived — not code-mirroring) and testCtPopLoneHighBit (exact count 1), both added in this PR; full suite 8/8 green on the unmutated baseline (nix develop github:rainlanguage/rainix#sol-shell -c forge test).
• Mutations applied (restore-verified after each):
  • CTPOP_M1 low nibble …55 → …54 → testMaskConstantsRederived FAILS with the exact corrupted value (deterministic kill); the fuzz/mutual-check tests also fail probabilistically because ctpop and ctpopSlow consume M1 through different formulas — the new pin makes the kill deterministic and value-level for all 9 constants, including M8–M128 which only ctpopSlow reads.
  • ctpop final shift >> 248 → >> 240 → testCtPopLoneHighBit FAILS (1 != 256), plus 4 pre-existing tests.
  • Restored → 8/8 PASS, clean tree.
• Oracle: Hamming-weight definition (the file's own Wikipedia reference) — the expected mask patterns (width set bits alternating with width clear, byte-wise 0x01 for H01) and the lone-high-bit count of 1 are derived from the definition, independent of the constants under test.
• Category check: [test-bare-src-import] [LOW] Test uses a bare src/ import (breaks when consumed as a soldeer dependency) #24 names the one bare src/ import in the repo's only test file (fixed); [unpinned-masks-shared-constant-blindspot] [LOW] Mask constants have no direct test pin; ctpop/ctpopSlow share M1/M2/M4 #25 asks for direct pins on the shared mask constants (all 9 pinned); [no-single-high-bit-test] [INFO] No deterministic lone-high-bit (1<<255) test #26 asks for the deterministic lone-high-bit case (added). Adversarial pass on the unit found no candidate bugs: the type(uint256).max special case is correct (the SWAR byte-sum overflows at count 256, which is exactly the excluded case).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests
  • Expanded verification of bit-counting behavior, including cases with only the highest bit set.
  • Added independent checks confirming that alternating-bit and single-bit mask constants are calculated correctly.
  • Improved coverage across all supported mask widths to help detect regressions in low-level counting utilities.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 75819f48-07e0-4328-be02-512450643378

📥 Commits

Reviewing files that changed from the base of the PR and between 208336a and 578de9f.

📒 Files selected for processing (1)

• test/src/lib/LibCtPop.ctpop.t.sol

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Walkthrough

The test suite imports the exported popcount masks, adds deterministic coverage for 1 << 255, and independently re-derives all mask constants, including CTPOP_H01.

Changes

Ctpop test coverage

Layer / File(s)	Summary
Mask and high-bit validation test/src/lib/LibCtPop.ctpop.t.sol	Imports CTPOP_M1 through CTPOP_M128 and CTPOP_H01, tests a lone high bit, and verifies each constant against an independently generated mask.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the three main changes: mask pinning, a lone-high-bit test, and the relative import fix.
Linked Issues check	✅ Passed	The PR addresses #24, #25, and #26 with the relative import, explicit mask re-derivation, and deterministic MSB-only coverage.
Out of Scope Changes check	✅ Passed	The visible changes stay within the linked testing and import-fix objectives and do not introduce unrelated scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 2026-07-18-test-hardening

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[thedavidmeister]

🤖 ai:vetter
Reviewed 5846438: ready — closes #24 #25 #26 — relative src import, all 9 mask constants pinned by independent loop re-derivation, deterministic lone-high-bit test; assertions hand-verified, mutation claims spot-checked
cost 212 — loop-derived mask pins, verify altMask math

[thedavidmeister]

Reviewed 578de9f: APPROVE

Closes #24, #25, #26. Verified by execution against the repo, not by reading the diff:

• [test-bare-src-import] [LOW] Test uses a bare src/ import (breaks when consumed as a soldeer dependency) #24 (bare src/ import) — fixed, and the CATEGORY is complete, not just the named line: only two .sol files exist repo-wide and this was the sole bare src/ import; remappings.txt carries no src/ self-remap, so the diagnosis (root-relative resolution breaks as a soldeer dependency) was correct. ../../../src/lib/LibCtPop.sol resolves correctly from test/src/lib/.
• [unpinned-masks-shared-constant-blindspot] [LOW] Mask constants have no direct test pin; ctpop/ctpopSlow share M1/M2/M4 #25 (mask constants unpinned) — proven discriminating by mutation, not inspection. Corrupting CTPOP_M4 (the shared mask) makes testMaskConstantsRederived fail directly, naming the exact constant mismatch — which is what the issue asked for ("fails directly rather than only via a downstream count mismatch"). The re-derivation is genuinely independent (loop arithmetic, never reads the constants); the width=128 and width=64 chunk offsets are correct. Mutation restored, suite back to 8/8 green.
• [no-single-high-bit-test] [INFO] No deterministic lone-high-bit (1<<255) test #26 (lone high bit) — added, and stronger than the issue's proposal: asserts both implementations return exactly 1 rather than merely agreeing.

Side note: under the CTPOP_M4 mutation the pre-existing n-oracle tests also failed, so #25's premise that the cross-check alone could not catch a shared-constant bug was slightly over-conservative. That does not diminish the change — its value is the direct, diagnostic pin, which it delivers.

audit/mutation-test-scans.json dropped in 578de9f: unrelated to the three issues and off-convention (audit/ is the Protofire PDF location that roh-scan scopes to audit/protofire/; the audit skill's stamps live in .audit/), and no other repo in the org carries that filename. Confirmed harmless either way — roh-scan globs audit/protofire/ only, and REUSE legal passes — but not worth establishing a new path by accident.

All checks green on this SHA (rainix legal/static/test, CodeRabbit); mergeStateStatus CLEAN.

Note: automated review, not human approval — merging on the maintainer's explicit instruction.

[thedavidmeister]

Correction — my removal of audit/mutation-test-scans.json in 578de9f was wrong.

I justified it with "no other repo in the org carries this filename". That is false. The file is an established convention, also present in rainlanguage/raindex and S01-Issuer/st0x.atomic-bridge with the same schema.

The mistake: a code search for the exact filename token returned empty silently, and I treated that as evidence of absence instead of checking a known repo. Searching adversarial-mutation finds all three immediately.

Restored in #32. The rest of this PR's review stands — the removal was the only part based on a bad premise.