test(bytes): add QuickCheck property tests

[bobzhang]

Adds bytes/quickcheck_test.mbt: model-based QuickCheck property tests for immutable Bytes and BytesView, checked against plain Array[Byte] reference implementations. moonbitlang/core/quickcheck was already in the package's for "test" imports, so no moon.pkg change; .mbti is untouched.

Property families

• Roundtrips — from_array/to_array identity; makei agrees with its generating function; from_iter, iter, iter2, get/at all agree with indexed model reads (including out-of-bounds get returning None).
• Concat / repeat — (a + b).to_array() equals model concatenation; length is additive; associativity; b"" is a two-sided identity; repeat(n) equals n-fold concatenation.
• View offset algebra (the focus) — for random valid (start, end) including empty/full/boundary slices: view contents equal the model slice element-for-element; data()/start_offset() bookkeeping is exact; view-of-view composes as b[i:j][k:l] == b[i+k : i+l] (verified both by Eq and against the model slice, plus a third nesting level); get_view mirrors the aborting slice on valid ranges and returns None on negative start / end past length / start > end; to_owned materializes exactly the viewed range; reading through views never disturbs the immutable parent.
• Unsigned ordering — Compare is shortlex and lexical_compare is pure lexicographic, both validated against unsigned-byte models with generation biased toward bytes >= 0x80 (where a signed-byte comparison bug would surface), plus an explicit 0x7F vs 0x80 boundary probe; a == b iff compare == 0 iff equal arrays; equal_to_bytes agrees with Eq.
• Hash consistency — equal Bytes hash equally; bs.hash() == bs[:].hash() (exercises the specialized non-JS Bytes::hash fast path against the BytesView hasher path); equal-content views at different offsets in different backing buffers hash equally.
• Search — find/rev_find vs naive scans over a 0x7E..0x81 boundary alphabet, with needles sliced from the haystack (guaranteed hits), aliased needles viewing the same backing bytes, perturbed needles (model decides), searches inside offset views, empty-pattern semantics, and long needles over dense false-candidate haystacks to drive the long-scanner and Rabin–Karp fallback paths; has_prefix/has_suffix/chop_prefix/chop_suffix vs the model, including through nonzero-offset views.

Verification

• moon check clean; moon info && moon fmt produce no .mbti or formatting diffs.
• moon test -p moonbitlang/core/bytes passes on wasm-gc, wasm, js, native (148 tests each).
• Locally swept seeds 1, 987654321, 20260814 at max_size=200 across backends before settling on the default seed — all passed.

Bugs found

None. The stressed areas (view offset bookkeeping under nesting and aliasing, unsigned comparison above 0x80, per-backend SIMD/scalar/Rabin–Karp search paths, hash fast-path consistency) all behaved per their documented semantics on every backend.

🤖 Generated with Claude Code

[coveralls]

Coverage Report for CI Build 6040

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Build has drifted: This PR's base is out of sync with its target branch, so coverage data may include unrelated changes.
Quick fix: rebase this PR. Learn more →

Coverage remained the same at 90.29%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	17642
Covered Lines:	15929
Line Coverage:	90.29%
Coverage Strength:	133985.55 hits per line

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💛 - Coveralls

[Copilot]

Pull request overview

Adds a new MoonBit QuickCheck test suite for Bytes / BytesView, using Array[Byte] as a reference model to validate a broad set of semantic properties (roundtrips, concatenation/repeat, view offset algebra, ordering/hash consistency, and search/prefix/suffix behavior) across backends.

Changes:

• Introduces model helper functions (imod, pick_range, slice/ordering/search models) to define backend-independent expectations.
• Adds property tests covering Bytes/BytesView construction, iteration/indexing, slicing/view composition, ordering semantics, hashing consistency, and search/prefix/suffix APIs.
• Adds targeted generators (boundary-crossing alphabets and biased byte tweaks) to stress byte-sign boundaries and dense match patterns.

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