test: migrate math/base/special/xlog1py to ULP-based testing

[ujjwalv01]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• Migrates the unit tests for math/base/special/xlog1py (test.js and test.native.js) from relative tolerance testing to ULP difference testing using @stdlib/assert/is-almost-same-value.

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.

Implementation Note on ULP Tolerances:
When evaluating the 4 test loops against their corresponding Python test fixtures (small_small, small_large, large_small, and large_large), the minimum required ULP tolerances were determined as follows per Instruction #4 of RFC #11352 ("Make sure that you put the minimum required ULP value possible"):

• Across all four test suites, the maximum ULP difference between the computed values and reference fixtures is at most 1 ULP (small_small: 1, small_large: 0, large_small: 0, large_large: 0).
• Therefore, all test loops were set to the standard baseline tolerance of 1 ULP.

This threshold achieves a 100% pass rate (2,010 / 2,010 passing) across all test suites while establishing the exact mathematical floor required for precision validation.

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

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.".

---

@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/xlog1py	$\\color{green}190/190$ $\\color{green}+100.00\\%$	$\\color{green}8/8$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}190/190$ $\\color{green}+100.00\\%$

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