test: migrate stats/base/dists/poisson/mgf 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 @stdlib/stats/base/dists/poisson/mgf from relative-tolerance assertions to ULP-based assertions using @stdlib/assert/is-almost-same-value, per the guidance in [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.
• updates test/test.mgf.js, test/test.factory.js, and test/test.native.js to mirror the idiom used in previously converted packages (e.g. stats/base/dists/normal/mgf, stats/base/dists/normal/mean, stats/base/dists/weibull/cdf).
• replaces the previous EPS * abs( expected[ i ] ) tolerance loops in all three files with t.strictEqual( isAlmostSameValue( y, expected[ i ], 0 ), true, 'returns expected value' ).
• drops the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires.

test/test.js only asserts on the main export and the attached factory method and thus required no changes.

The tightest ULP bound was determined empirically by measuring, for every fixture value, the minimum N for which isAlmostSameValue( actual, expected, N ) returns true, and taking the maximum over the full Julia fixture set (3000 values across the small, medium, and large fixtures):

• test/test.mgf.js: N = 0 ULP (measured maximum ULP difference: 0 across all three fixture groups).
• test/test.factory.js: N = 0 ULP (measured maximum ULP difference: 0 across all three fixture groups).
• test/test.native.js: N = 0 ULP, mirroring the JavaScript bound, consistent with previously merged conversions.

All 3000 fixture values match the Julia reference bit-for-bit, so 0 is both the measured maximum and the tightest bound expressible, and the previous tolerance branch was never taken.

test/test.js, test/test.mgf.js, and test/test.factory.js were each run twice at the final N = 0 (3, 3008, and 3009 assertions, respectively; all passing) to confirm the bound is deterministic. Linting with the repository's etc/eslint/.eslintrc.tests.js configuration is clean for all four test files, and only the three test files are changed.

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 native add-on could not be built in the environment used to author this PR, so test/test.native.js was exercised in skipped form only and its N = 0 bound is mirrored from the JavaScript measurement rather than measured against the C implementation. Reviewers may wish to confirm the native tests pass at N = 0 in an environment with add-ons built. This is the main reason the PR is opened as a draft.

Other

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

No.

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 authored by Claude Code (Anthropic) running as an unattended scheduled task. The conversion mirrors the exact idiom used in previously merged ULP migrations authored by the PR author (e.g. #14302, #14472), and the ULP bound was measured empirically against the existing Julia fixtures for the JavaScript implementation.

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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/poisson/mgf	$\\color{green}246/246$ $\\color{green}+100.00\\%$	$\\color{green}15/15$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}246/246$ $\\color{green}+100.00\\%$

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