test: migrate stats/base/dists/weibull/kurtosis 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/weibull/kurtosis from relative tolerance testing to ULP difference testing, per [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.

Specifically, in both test/test.js and test/test.native.js:

• adds the @stdlib/assert/is-almost-same-value require and removes the now unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires.
• removes the delta and tol declarations and the computed tolerance logic (tol = 1.5e6 * EPS * abs( expected[ i ] )).
• replaces the y === expected[i] / t.ok( delta <= tol, ... ) branch with a single t.strictEqual( isAlmostSameValue( y, expected[ i ], 1292760 ), true, 'returns expected value' );.

ULP constant: 1292760 (same value in test/test.js and test/test.native.js).

This is the measured minimum. Starting from a high bound and tightening over the full 500-case Julia fixture set, 1292760 is the smallest integer for which every case passes:

ULP bound	failing fixtures
1292758	1
1292759	1
1292760	0

The worst case is k = 19.094404848351264, lambda = 17.223983273178845, where the implementation returns 1.2261287913603294 against an expected 1.226128791073279 (a relative difference of ~2.3e-10, consistent with the previous 1.5e6 * EPS relative tolerance).

The JavaScript and C implementations require the identical bound (both measured at 1292760), so a single constant is used in both 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?

The required bound here is large (1292760), inherited from the package's pre-existing 1.5e6 * EPS relative tolerance rather than introduced by this change. It is within the range of bounds already used elsewhere in the codebase after migration. Happy to revisit if maintainers would prefer the underlying accuracy of the implementation be addressed first, in which case this migration could wait.

Other

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

Verification performed:

• make test TESTS_FILTER=".*/stats/base/dists/weibull/kurtosis/.*" — 514/514 passing in test/test.js.
• The native addon was built locally (node-gyp rebuild) so that test/test.native.js was actually exercised rather than skipped — also 514/514 passing.
• The suite was run twice at the final bound; results were identical across runs (no FMA/arch-dependent variation observed).
• make eslint-tests TESTS_FILTER=".*/stats/base/dists/weibull/kurtosis/.*" — clean.
• Only the two test files are modified; no changes to the implementation, fixtures, or docs.

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 helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

This PR was authored by Claude Code running as an unattended scheduled task. It studied the idiom established in previously merged migrations (notably the sibling stats/base/dists/weibull/skewness, #15484, and stats/base/dists/geometric/mean, #15491, for the EPS-require removal), applied the same mechanical transformation here, and determined the ULP bound empirically by measuring the required ULP distance across the full fixture set rather than by guessing and re-running.

---

@stdlib-js/reviewers

---

Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/weibull/kurtosis	$\\color{green}208/208$ $\\color{green}+100.00\\%$	$\\color{green}10/10$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}208/208$ $\\color{green}+100.00\\%$

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