test: migrate stats/incr/mmeanabs2 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/incr/mmeanabs2 from a computed relative-tolerance comparison (delta = abs( expected - actual ) / tol = 1.0 * EPS * abs( expected ), asserted via t.strictEqual( delta <= tol, ... )) to a ULP-difference assertion using @stdlib/assert/is-almost-same-value.
• applies the migration to the single tolerance-based assertion site in test/test.js. The package has no test/test.native.js. The remaining assertions in the file are exact comparisons against null, thrown TypeErrors, function types, NaN, and the exactly representable values 17.0 and 9.8596, which are correct as-is and are left unchanged.
• removes the now-unused @stdlib/math/base/special/abs and @stdlib/constants/float64/eps requires, along with the delta and tol variable declarations.
• collapses the if ( actual === expected[i] ) { ... } else { ... } branch in the moving-mean-of-squared-absolute-values test into a single ULP assertion, matching the migrated idiom.

Only a test file is changed; no implementation, fixture, or documentation changes are included.

ULP bounds

Assertion	Previous tolerance	ULP bound
moving arithmetic mean of squared absolute values computed incrementally (6 values)	1.0 * EPS * abs( expected )	1

This is the minimum integer bound N such that isAlmostSameValue( actual, expected[ i ], N ) holds at every element of the fixture. It was measured by starting from a high bound (64, which passes) and tightening, computing the per-element ULP distance directly outside the test harness and then confirming through the test suite: at N = 1 the suite is 41/41 passing, and at N = 0 three assertions fail (38/41), so no tighter bound exists.

The per-element ULP differences are 0, 0, 0, 1, 1, 1. The first three expected values (4.0, 6.5, 17.0/3.0) are reproduced bit-for-bit, while the last three (29.0/3.0, 29.0/3.0, 41.0/3.0) differ by one ULP: the accumulator computes the window mean incrementally rather than as a single division, so it returns 9.666666666666668 where the literal expression 29.0/3.0 rounds to 9.666666666666666. The original test anticipated this by branching on actual === expected[i] and falling back to a relative tolerance for the inexact cases.

make test TESTS_FILTER=".*/stats/incr/mmeanabs2/.*" was run twice at the final bound with identical results: 41/41 passing on both runs, no failures, ruling out FMA/architecture-dependent flakiness on this platform. make eslint-tests TESTS_FILTER=".*/stats/incr/mmeanabs2/.*" is clean.

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.

The resulting diff mirrors the already-merged migrations for the sibling accumulator packages stats/incr/mmape (#15150), stats/incr/mda (#15142), and stats/incr/nanmrss (#15166), which share the same test structure.

Two environment notes, neither of which affected verification:

• make install-node-modules initially failed with ETARGET for es-object-atoms@^1.1.2. The version does exist in the registry (published 2026-05-22); the local npm packument cache was stale and served a filtered view. After npm cache clean --force, the install completed and the full toolchain was available for this PR.
• The pre-commit hook's lint-editorconfig-files step could not run, because it downloads the editorconfig-checker binary from a GitHub release that this environment cannot reach. The changed file was instead checked manually against .editorconfig: LF line endings, tab indentation, no trailing whitespace, and a final newline.

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 primarily by Claude Code, running as an unattended scheduled task. It selected the package, studied previously migrated packages in the same family to match the established idiom, performed the migration, and determined the minimum passing ULP bound empirically at the assertion site.

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/mmeanabs2	$\\color{green}141/141$ $\\color{green}+100.00\\%$	$\\color{green}8/8$ $\\color{green}+100.00\\%$	$\\color{green}2/2$ $\\color{green}+100.00\\%$	$\\color{green}141/141$ $\\color{green}+100.00\\%$

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