test: migrate stats/base/dists/negative-binomial/logpmf 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/negative-binomial/logpmf from relative tolerance testing to ULP difference testing, replacing the computed delta/tol comparisons with @stdlib/assert/is-almost-same-value.
• removes the now unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires and the associated delta/tol local variables.
• applies the same changes to both test/test.factory.js and test/test.logpmf.js (test/test.js only asserts exports and required no changes).

The ULP bounds were tightened to the minimum value which still passes over the full fixture sets (each fixture set contains 1000 values, and the factory and main entry points require identical bounds):

Fixture set	Assertion	Previous tolerance	Final ULP	Measured minimum
small_small.json	small r and p	10.0 * EPS * abs( expected )	6	6 (fails at 5; worst case x = 13, r = 9, p = 0.135318550619653)
small_high.json	small r, large p	40.0 * EPS * abs( expected )	57	57 (fails at 56; worst case x = 0, r = 8, p = 0.9868792801820985)
high_small.json	large r, small p	10.0 * EPS * abs( expected )	9	9 (fails at 8; worst case x = 39, r = 14, p = 0.12604764008592798)
high_high.json	large r and p	80.0 * EPS * abs( expected )	109	109 (fails at 108; worst case x = 1, r = 93, p = 0.8327586644536866)

The larger bounds correspond to fixtures whose expected values are log-probabilities close to zero, where the relative tolerance expressed in ULPs is necessarily looser.

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 notes:

• make test TESTS_FILTER=".*/stats/base/dists/negative-binomial/logpmf/.*" passes: 4026 assertions in test/test.factory.js, 4020 in test/test.logpmf.js, and 3 in test/test.js, with no failures. The suite was run twice at the final ULP values with identical results, in order to rule out FMA/architecture-dependent flakiness.
• Tightness was confirmed by re-evaluating every fixture set at N-1 ULP; each set fails at N-1, so none of the four bounds can be lowered further.
• make lint-javascript-tests TESTS_FILTER=".*/stats/base/dists/negative-binomial/logpmf/.*" is clean.
• The package has no native implementation, so there is no test/test.native.js to update.
• Only the two test files are changed.

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

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• Code generation (e.g., when writing an implementation or fixing a bug)
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Disclosure

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance. This helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

This PR was written by Claude Code, running as an unattended scheduled task. The conversion mirrors the idiom established in previously merged migration commits, and the ULP bounds were determined empirically rather than guessed.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/negative-binomial/logpmf	$\\color{red}523/566$ $\\color{green}+92.40\\%$	$\\color{red}45/51$ $\\color{green}+88.24\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{red}523/566$ $\\color{green}+92.40\\%$

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

[Planeshifter]

⚠️ Issue Reference Review

An automated check found potentially unrelated issue/PR references in this PR:

Reference	Assessment	Reasoning
#11352	suspicious	#11352 is an RFC/tracking issue explicitly scoped to migrating math/base/special packages from relative-tolerance to ULP-based testing (its own instructions repeatedly say "a package in math/base/special" and "please only update the tests for a single package" within that namespace). This PR instead migrates tests for stats/base/dists/negative-binomial/logpmf, which falls outside the issue's stated scope, even though it applies the same general ULP-testing technique.

Why this matters: GitHub automatically closes issues referenced with
closing keywords (Resolves, Closes, Fixes) when the PR is merged. Incorrect
references can accidentally close unrelated issues.

What to do:

• If the reference is correct, no action needed. This check may produce
  false positives.
• If the reference is incorrect, please update your PR description.

This assessment was generated by an AI model and is informational only.

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