test: migrate stats/base/dists/arcsine/logcdf to ULP-based assertions

[kgryte]

Description

What is the purpose of this pull request?

This pull request:

• migrates the tests for stats/base/dists/arcsine/logcdf from relative tolerance (EPS-scaled) comparisons to ULP-based assertions using @stdlib/assert/is-almost-same-value, per [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.

Affected files: test/test.logcdf.js and test/test.factory.js. The package has no test/test.native.js, and test/test.js contains only exact export assertions and is left unchanged.

Each fixture loop of the form

if ( y === expected[i] ) {
    t.strictEqual( y, expected[i], ... );
} else {
    delta = abs( y - expected[ i ] );
    tol = 20.0 * EPS * abs( expected[ i ] );
    t.ok( delta <= tol, ... );
}

is replaced by

t.strictEqual( isAlmostSameValue( y, expected[i], <ulps> ), true, 'returns expected value' );

and the now-unused abs/EPS requires and delta/tol locals are removed.

ULP bounds. Mirroring the surrounding stats/base/dists conversions, each fixture group uses its own bound, tightened to the measured minimum that passes over the full fixture set (1000 values per fixture, identical for the main and factory code paths):

Fixture	Previous tolerance	ULP bound
small_range.json	20.0 * EPS * abs( expected[i] )	18
medium_range.json	20.0 * EPS * abs( expected[i] )	19
large_range.json	30.0 * EPS * abs( expected[i] )	33

These are minimal: decrementing any of the three bounds to 17 / 18 / 32 fails exactly one assertion in each corresponding group, in both test.logcdf.js and test.factory.js.

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.

Verification performed locally on linux/x64, Node.js v22:

• test/test.logcdf.js (3011 assertions), test/test.factory.js (3016 assertions), and test/test.js (3 assertions) all pass. The suite was run twice at the final bounds with identical results, to rule out FMA/arch-dependent flakiness.
• make eslint-tests TESTS_FILTER=".*/stats/base/dists/arcsine/logcdf/.*" is clean.
• Only the two test files are modified; no source, fixture, or documentation changes.

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, which performed the test migration, measured the minimum ULP bounds against the fixtures, and ran the test and lint checks.

---

@stdlib-js/reviewers

---

Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/arcsine/logcdf	$\\color{green}237/237$ $\\color{green}+100.00\\%$	$\\color{green}25/25$ $\\color{green}+100.00\\%$	$\\color{green}3/3$ $\\color{green}+100.00\\%$	$\\color{green}237/237$ $\\color{green}+100.00\\%$

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