test: migrate stats/base/dists/chisquare/quantile to ULP-based assertions

[kgryte]

Description

What is the purpose of this pull request?

This pull request:

• migrates the test suite of stats/base/dists/chisquare/quantile from computed relative-tolerance comparisons to ULP-based assertions, per [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.
• replaces the if ( y === expected[i] ) { ... } else { delta = abs( y - expected[i] ); tol = 250.0 * EPS * abs( expected[i] ); t.ok( delta <= tol, ... ); } branches in test/test.quantile.js and test/test.factory.js with a single t.strictEqual( isAlmostSameValue( y, expected[ i ], 402 ), true, 'returns expected value' ); assertion.
• 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, along with the delta/tol declarations.

ULP bound

• Final ULP constant: 402 (used in both test/test.quantile.js and test/test.factory.js).
• 402 is the measured minimum. It was determined by bisecting the ULP bound over the complete 5000-point test/fixtures/julia/decimal_decimal.json fixture set for both the main export and the function returned by factory. Both code paths have the same worst-case point (fixture index 4815).
• Minimality was verified empirically: at N = 402 the suite reports 10029 passing assertions and 0 failures; at N = 401 exactly 2 assertions fail (the worst-case point in each of the two files).
• The suite was run three times at the final N = 402 with identical results, confirming the bound is not sensitive to FMA/arch variation on this platform.
• For reference, the previous tolerance was 250.0 * EPS * abs( expected[i] ), so a bound in the low hundreds of ULP is consistent with the accuracy this suite previously accepted.

Verification

• node_modules/.bin/tape lib/node_modules/@stdlib/stats/base/dists/chisquare/quantile/test/*.js → # tests 10029 / # pass 10029 / # ok (three consecutive runs).
• make eslint-tests TESTS_FILTER=".*/stats/base/dists/chisquare/quantile/.*" → clean, exit 0.
• Only the two test files are modified; no source, documentation, benchmark, or fixture files are touched.

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?

• 402 ULP is on the larger end of the bounds used elsewhere in the repo, but it is the tightest value that passes the existing fixtures and is in line with the suite's previous 250 * EPS relative tolerance. If reviewers would prefer the underlying accuracy be investigated rather than codified, happy to split that out into a separate issue.

Other

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

• The idiom follows the convention already settled on in this family of packages (e.g. stats/base/dists/erlang/quantile, stats/base/dists/gumbel/quantile): an inline numeric ULP literal rather than a named constant, and the standardized 'returns expected value' assertion message.
• The repository's pre-commit EditorConfig hook could not run in this environment, because it downloads the editorconfig-checker binary from a GitHub repository outside this session's allowed scope. EditorConfig conformance was therefore checked manually for both files: LF line endings, UTF-8, tab indentation, no trailing whitespace, and a single 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 by Claude Code running as an unattended scheduled task. It selected the package, mirrored the conversion idiom from previously merged PRs in the same family, measured the minimum ULP bound by bisection over the fixture set, and verified the tests and linting.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Hello! 👋

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/chisquare/quantile	$\\color{green}180/180$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}180/180$ $\\color{green}+100.00\\%$

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