test: migrate stats/base/dists/beta/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/beta/kurtosis from computed relative-tolerance comparisons (delta = abs( y - expected[ i ] ) / tol = 1.0 * EPS * abs( expected[ i ] ), asserted via t.ok( delta <= tol, ... )) to ULP-difference assertions using @stdlib/assert/is-almost-same-value.
• applies the migration to the two tolerance-based assertion sites in the package: one in test/test.js (JavaScript implementation) and one in test/test.native.js (C implementation). Both iterate over the same 1000-point test/fixtures/julia/data.json fixture.
• collapses the if ( y === expected[i] ) { ... } else { ... } branch at each site into a single ULP assertion, and standardizes the assertion message to 'returns expected value'.
• removes the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires and the delta and tol variable declarations.

The remaining assertions in these files are exact comparisons (NaN propagation for NaN, non-positive, and infinite parameters, along with function type checks), which are correct as-is and are left unchanged.

Only test files are changed; no implementation, fixture, or documentation changes are included.

ULP bounds

File	Implementation	Previous tolerance	ULP bound
test/test.js	JavaScript, main export	1.0 * EPS * abs( expected )	0
test/test.native.js	C	2.0 * EPS * abs( expected )	0

0 is the minimum bound N such that isAlmostSameValue( y, expected[ i ], N ) === true at every element of the fixture, and is thus the tightest bound possible. It was determined by computing the per-element ULP distance directly outside the test harness over the full 1000-point fixture: every fixture point is reproduced bit-for-bit by both implementations, so the maximum ULP distance is 0 for each. The previous relative tolerances (1.0 * EPS and 2.0 * EPS) permitted a non-exact result, so the new bound is tighter than the tolerance it replaces rather than a loosening of the existing test.

The excess kurtosis is evaluated as a short sequence of multiplications, additions, and a single division, and the JavaScript and C implementations perform those operations in the same order, which is why both agree exactly with the Julia reference across the fixture.

make test TESTS_FILTER=".*/stats/base/dists/beta/kurtosis/.*" was run twice at the final bound with identical results on both runs (1014 assertions in each of the two test files, 2028 in total, no failures and no skips), ruling out FMA/architecture-dependent flakiness on this platform. The native add-on was built locally (node-gyp rebuild) so that test.native.js actually executed rather than being skipped. make eslint-tests TESTS_FILTER=".*/stats/base/dists/beta/kurtosis/.*" is clean, as is make lint-license-headers-files for the changed 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.

The resulting diff mirrors the already-merged migrations for the sibling distribution packages stats/base/dists/beta/skewness, stats/base/dists/beta/variance, and stats/base/dists/beta/stdev, which share the same test structure and, in the first two cases, the same 0 ULP bound.

Two environment notes, neither of which affected verification:

• make install-node-modules initially failed with ETARGET for es-object-atoms@^1.1.2. The local npm packument cache was stale and served a filtered view of the registry; after npm cache clean --force, the install and make init completed and the full toolchain was available for this PR.
• The pre-commit hook's lint-editorconfig-files step could not run, because it downloads the editorconfig-checker binary from a GitHub release that this environment cannot reach. The changed files were instead checked manually against .editorconfig: LF line endings, tab indentation, no trailing whitespace, and a final newline.

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

This PR was written primarily by Claude Code, running as an unattended scheduled task. It selected the package, studied previously migrated packages in the same family to match the established idiom, performed the migration, and determined the minimum passing ULP bound empirically over the full fixture set.

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@stdlib-js/reviewers

🤖 Generated with Claude Code

https://claude.ai/code/session_018pww2eTE6dBtB2G1jEpVDr

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/beta/kurtosis	$\\color{green}207/207$ $\\color{green}+100.00\\%$	$\\color{green}10/10$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}207/207$ $\\color{green}+100.00\\%$

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