test: migrate stats/base/dists/hypergeometric/variance to ULP-based assertions

[kgryte]

Description

What is the purpose of this pull request?

This pull request:

• migrates the tests for stats/base/dists/hypergeometric/variance from computed relative-tolerance comparisons (delta/tol against 18.0 * EPS * abs( expected[ i ] )) 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.
• removes the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires from both test files.

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

ULP bounds

The JavaScript and C implementations evaluate the same variance formula using different associations, so they need different bounds:

File	Implementation	Expression	ULP bound
test/test.js	JavaScript	n * ( K/N ) * ( (N-K)/N ) * ( (N-n)/(N-1) )	29
test/test.native.js	C	n * p * ( 1.0-p ) * ( (N-n)/(N-1) )	1

The C association matches the one used by the Julia reference implementation (Distributions.var( Hypergeometric( K, N-K, n ) )) that generated test/fixtures/julia/data.json, which is why the native bound is much tighter than the JavaScript one.

Both values are the measured minima over the full 100-point fixture set:

• test/test.js passes at 29 and fails at 28 (worst case: N = 60, K = 59, n = 32).
• test/test.native.js passes at 1 and fails at 0.

Each suite was run twice at its final bound with identical results. The native add-on was built locally (node-gyp configure build) so that test.native.js actually executed rather than being skipped; its 108 assertions pass. The native results were additionally checked to be unchanged under FMA contraction (-march=native), so the 1 ULP bound is not sensitive to compiler contraction on this expression.

Reviewers may wish to note that the 29 ULP figure reflects the JavaScript implementation's association rather than a defect in the tests; tightening it would require changing lib/main.js, which is out of scope for this PR.

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?

• Is a 29 ULP bound for test.js acceptable, or would you prefer the JavaScript implementation be re-associated to match the C implementation (and the Julia reference) in a separate PR so that both bounds can be tightened to 1?

Other

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

The pre-commit static analysis hook could not run in this environment because it attempts to download the editorconfig-checker binary from GitHub releases, which was not reachable. EditorConfig compliance (LF endings, tab indentation, no trailing whitespace, final newline) and eslint -c etc/eslint/.eslintrc.tests.js were both verified manually instead; ESLint reports no problems for either file.

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 converted packages to match the established idiom, performed the conversion, and determined the minimum passing ULP bounds empirically by bisecting on the full fixture set.

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@stdlib-js/reviewers

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/hypergeometric/variance	$\\color{green}202/202$ $\\color{green}+100.00\\%$	$\\color{green}13/13$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}202/202$ $\\color{green}+100.00\\%$

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