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

[Planeshifter]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates test/test.js and test/test.native.js of math/base/special/rcbrt from relative-tolerance (EPS-based) assertions to the ULP-based testing convention of [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352.
• computes the minimum required ULP value per fixture block via direct ULP-difference computation (@stdlib/number/float64/base/ulp-difference) over all test fixtures. Every fixture block (8 positive blocks × 5003 cases, 6 negative blocks × 503 cases) has a maximum ULP difference of 0: both the JavaScript and native (C) results are bit-identical to the Julia reference fixtures. Accordingly, per the migration convention, all migrated assertions use plain t.strictEqual( y, expected[ i ], 'returns expected value' ); rather than isAlmostSameValue, and the now-unused EPS and abs requires and delta/tol variables were removed.
• collapses the obsolete exact-equality if/else short-circuit branches into the single exact assertion.

Native results did not diverge from the JavaScript results (all native assertions pass with exact equality), so no native-specific larger tolerances (and no accompanying NOTE comments) were needed.

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?

Since all fixture values match exactly, this migration removes tolerance testing for this package entirely (exact equality) rather than introducing isAlmostSameValue. Flagging for maintainer awareness in case looser tolerances are preferred for cross-platform native builds.

Other

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

Minimum ULP values were independently re-verified by a second pass which recomputed the maximum ULP difference per fixture block; all blocks confirmed at 0. JavaScript tests pass via the official harness (make test), and the native add-on was built and all native test assertions pass locally.

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 as part of an automated migration of math/base/special test suites to ULP-based testing (issue #11352), including automated minimum-ULP discovery and an independent adversarial verification pass; the changes were reviewed before submission.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/rcbrt	$\\color{green}186/186$ $\\color{green}+100.00\\%$	$\\color{green}5/5$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}186/186$ $\\color{green}+100.00\\%$

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