[derive] Refactor is_bit_valid tests

[joshlf]

---

• 　 [derive] Allow TryFromBytes on non-Immutable unions #2876
• 　 [WIP] Use ReadOnly in is_bit_valid #2873
• 　 [WIP] ReadOnly #2866
• 　 Make SizeEq safe, introduce CastExact #2872
• 👉 [derive] Refactor is_bit_valid tests #2879

Latest Update: v4 — Compare vs v3

📚 Full Patch History

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v4	vs v3	vs v2	vs v1	vs Base
v3		vs v2	vs v1	vs Base
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[gemini-code-assist]

Summary of Changes

Hello @joshlf, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on refactoring the is_bit_valid tests within the zerocopy-derive crate. The primary goal is to enhance the clarity and maintainability of the test suite by abstracting repetitive test setup and assertion logic into a reusable helper function. This change improves the overall structure of the tests without altering the functional behavior of the is_bit_valid implementations.

Highlights

• New Test Helper Function: A new public helper function, test_is_bit_valid, has been introduced in zerocopy-derive/tests/include.rs. This function centralizes the common logic for testing the is_bit_valid method of types implementing TryFromBytes, including pointer manipulation and assertion.
• Test Refactoring: Existing is_bit_valid tests in zerocopy-derive/tests/struct_try_from_bytes.rs and zerocopy-derive/tests/union_try_from_bytes.rs have been refactored to utilize the new test_is_bit_valid helper. This significantly reduces boilerplate code and improves test readability and maintainability.
• Trait Derives Added: To accommodate the new test helper's requirements, imp::Immutable and imp::IntoBytes derives were added to several test structs and unions (e.g., One, Two, MaybeFromBytes) in the struct_try_from_bytes.rs and union_try_from_bytes.rs test files.
• Consolidated Test Cases: Some redundant test cases, such as two_bad in both struct_try_from_bytes.rs and union_try_from_bytes.rs, were removed and their logic integrated into the main two test using the new helper, further streamlining the test suite.

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[gemini-code-assist]

Code Review

This pull request introduces a significant refactoring of the is_bit_valid tests by creating a new helper function, test_is_bit_valid. This change greatly simplifies the test suite, removing boilerplate code and making the tests more readable and maintainable. The new helper is correctly applied across struct and union tests. My review includes one suggestion to improve the clarity of a safety comment in the new test helper.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (5e71c61) to head (59f812e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2879   +/-   ##
=======================================
  Coverage   91.90%   91.90%           
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  Files          20       20           
  Lines        5878     5878           
=======================================
  Hits         5402     5402           
  Misses        476      476           

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