test: migrate stats/base/dists/frechet/mean to ULP-based assertions

[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates the tests for stats/base/dists/frechet/mean from relative-tolerance assertions (delta <= tol, with delta = abs( y - expected[ i ] ) and tol = 2.0 * EPS * abs( expected[ i ] )) to ULP-difference assertions using @stdlib/assert/is-almost-same-value.
• applies the same migration to both test/test.js and test/test.native.js.
• preserves all existing test cases and structure, including the non-tolerance assertions (NaN parameters, nonpositive alpha, and nonpositive s) and the expected[ i ] !== null fixture guard.

The ULP bound used is:

Test file	Fixture block	ULP
test/test.js	fixtures/julia/data.json (81 non-null cases)	3
test/test.native.js	fixtures/julia/data.json (81 non-null cases)	3

3 is the measured minimum: starting from N = 64 and tightening, N = 3 passes over the full fixture set while N = 2 fails (one fixture entry, alpha = 3.988247436421993, s = 2.814258823431831, differs from the Julia expected value by exactly 3 ULP). The suite was run twice at the final N to confirm deterministic passing (96 assertions, all passing on both runs).

Because the native add-on is not built in this environment, test/test.native.js is skipped locally and its bound could not be measured by running that file directly. Instead, the C implementation was compiled standalone against its resolved C dependency closure (math/base/special/gamma, math/base/assert/is-nan, constants/float64/pinf) and evaluated over all 100 fixture inputs: its results are bit-for-bit identical to the JavaScript implementation for every input, so the same bound of 3 applies to both files.

Linting was checked before and after the change and is unchanged (0 errors; the same 2 pre-existing @cspell/spellchecker warnings for "Fréchet" in the test descriptions, which this PR does not touch). The only files changed are the two test files.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance.

This PR was authored by Claude Code: the assistant mechanically converted the tolerance-based assertions to isAlmostSameValue, agentically searched for the minimum ULP bound, verified that the C implementation matches the JavaScript implementation bit-for-bit over the fixture set, confirmed determinism across two full runs, and ran the local lint and test suites before submitting.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Hello! 👋

We've noticed that you've been opening a number of PRs addressing good first issues. Thank you for your interest and enthusiasm!

Now that you've made a few contributions, we suggest no longer working on good first issues. Instead, we encourage you to prioritize cleaning up any PRs which have yet to be merged and then proceed to work on more involved tasks.

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For ideas for future PRs, feel free to search the codebase for TODOs and FIXMEs and be sure to check out other open issues on the issue tracker. Cheers!

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/frechet/mean	$\\color{green}193/193$ $\\color{green}+100.00\\%$	$\\color{green}13/13$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}193/193$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.