test: migrate stats/base/dists/triangular/logpdf 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/triangular/logpdf from relative tolerance testing to ULP difference testing.
• replaces the if ( y === expected[i] ) { ... } else { delta/tol ... } branches and the t.ok( delta <= tol, ... ) assertions with t.strictEqual( isAlmostSameValue( y, expected[ i ], N ), true, 'returns expected value' );.
• adds a @stdlib/assert/is-almost-same-value import and removes the now unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps imports. The @stdlib/math/base/special/ln import is retained, as it is still used by the x = c test.

Final ULP constants

Each of the three fixture sets (small_range.json, medium_range.json, large_range.json, 1000 values each) is asserted with its own bound. Starting from a high bound and tightening, the measured minimum per fixture set and per test file is:

File	small range	medium range	large range
test/test.logpdf.js	55	52	83
test/test.factory.js	55	76	83
test/test.native.js	39	76	83

Every one of these nine bounds is the measured minimum: decrementing any one of them by 1 causes exactly one assertion in that fixture set to fail. The bounds are comparatively large because the fixture values are logarithms close to zero (the worst cases sit near ±0.007), so the pre-existing 40/60/50 * EPS relative tolerances already corresponded to tens of ULP at that magnitude.

The bounds differ slightly between the JS main export, the factory-created function, and the C implementation. This mirrors other migrated distribution packages where the JS and C results differ for the same inputs (e.g. stats/base/dists/betaprime/logcdf, stats/base/dists/f/quantile, stats/base/dists/gamma/quantile), per the FAQ.

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 performed locally:

• make test TESTS_FILTER=".*/stats/base/dists/triangular/logpdf/.*" → 9067 passing, 0 failing, run twice at the final bounds with identical per-file counts, to confirm determinism.
• The native add-on was built locally for this package so that test/test.native.js executed rather than being skipped; its bounds were therefore measured, not assumed. The build artifacts were removed before committing.
• eslint -c etc/eslint/.eslintrc.tests.js on the three changed files → clean.
• Only the three test files are changed; no implementation, fixture, docs, or package metadata files are touched.

The idiom follows the already-converted sibling package stats/base/dists/triangular/logcdf, which has the identical test-file layout.

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.".

This PR was authored by Claude Code. The migration mirrors the idiom established in the sibling package stats/base/dists/triangular/logcdf, and every ULP bound was measured empirically over the full fixture set (and shown to be minimal) rather than assumed.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/dists/triangular/logpdf	$\\color{green}355/355$ $\\color{green}+100.00\\%$	$\\color{green}39/39$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}355/355$ $\\color{green}+100.00\\%$

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