test: migrate stats/incr/apcorr to ULP-based assertions

[kgryte]

Resolves a part of #11352.

Description

What is the purpose of this pull request?

This pull request:

• migrates the test suite for stats/incr/apcorr from computed relative-tolerance assertions to ULP-based assertions using @stdlib/assert/is-almost-same-value.

Specifically, in test/test.js:

• adds the @stdlib/assert/is-almost-same-value require and drops the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires.
• removes the delta/tol variables and the actual === expected[ i ] branch in the two accumulator fixture loops.
• replaces the tolerance checks with t.strictEqual( isAlmostSameValue( actual, expected[ i ], <ULP> ), true, 'returns expected value' );.

ULP bounds

Each bound was tightened to the measured minimum integer which still passes over the full set of test values. The minimum was measured per test value, and confirmed by re-running the suite with each bound decremented by one (which fails, 6 assertions):

Test	Previous tolerance	Final ULP bound	Measured minimum
the accumulator function incrementally computes a sample absolute correlation coefficient	3.7 * EPS * abs( expected )	4	4
the accumulator function incrementally computes a sample absolute correlation coefficient (known means)	EPS * abs( expected )	1	1

The suite was run twice at the final bounds to confirm determinism (96 passing, 0 failing on both runs).

No other assertions were changed; the existing exact t.strictEqual comparisons (null, 0.0, NaN, and the two exactly-reproduced accumulator values) are left as-is, and no non-test files are touched.

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: make test TESTS_FILTER=".*/@stdlib/stats/incr/apcorr/.*" → 96 passing, 0 failing; eslint --config etc/eslint/.eslintrc.tests.js on the changed file is clean.
• The lint-editorconfig-files pre-commit step could not run in the authoring environment because the editorconfig-checker binary download was blocked by network policy, so EditorConfig conformance (tabs, LF line endings, no trailing whitespace, final newline) was verified manually instead. CI should be treated as authoritative here.

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, running unattended as a scheduled task. Claude Code studied the already-migrated sibling packages under stats/incr to mirror the established idiom, applied the mechanical substitution to test/test.js, and determined the minimum passing ULP bounds empirically.

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🤖 Generated with Claude Code

https://claude.ai/code/session_015maoYHf9sFNS4w6oCmCo5b

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/apcorr	$\\color{green}149/149$ $\\color{green}+100.00\\%$	$\\color{green}15/15$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}149/149$ $\\color{green}+100.00\\%$

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