[test][avatar] Add axe tests and WCAG conformance report

[michelengelen]

Adds axe coverage and the WCAG 2.2 Level A/AA conformance report for Avatar, plus an a11y-only fixture for image avatars.

Result	Count
✅ Supports	9
⚠️ Partially Supports	2
❌ Does Not Support	0
➖ Not Applicable	44

Known gaps: default letter/fallback avatars render white on grey[400] (~1.9:1) (1.4.3), and meaningful icon avatars fall below 3:1 (1.4.11).

Report: Avatar/accessibility.md

Important

How to review this PR

Layer 4 of 14 in a stacked series (#48915 → #48926). Its branch is built on a11y/stack/button (#48916). GitHub cannot chain PR bases across a fork, so every PR in the series targets master instead.

Review only the last commit — 1482433. Everything above it belongs to the layers below, and disappears as those merge.

Original work by @mj12albert. Supersedes #48732, rebased onto current master.

Part of the WCAG conformance effort (#14187).

[code-infra-dashboard]

Deploy preview

• docs/data/material/components/avatars/AvatarA11yImage.js

  
  

Bundle size

Bundle	Parsed size	Gzip size
@mui/material	0B(0.00%)	0B(0.00%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/private-theming	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

Details of bundle changes

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[michelengelen]

PR review

Nothing merge-blocking. The unit tests are precise (fallback icon hidden, decorative SvgIcon hidden) and the two-layer demoMeta rules resolve correctly under last-match-wins. One redundancy against the css-layout suite and one optional hardening.

Simplifications (1)

1. 🟡 The bespoke Avatar 1.4.12 test duplicates the css-layout suite

Location: test/regressions/index.test.js:353

describe('Avatar', () => {
  test('1.4.12 Text Spacing: initials stay visible under the WCAG overrides', ...

#48936, earlier in this stack, already runs 1.4.12 on /docs-components-avatars/LetterAvatars through CSS_LAYOUT_SUITES — same spacing overrides, same range-vs-box clip math, same 0.5px tolerance. The report's citation ("Confirmed by a Playwright regression test in test/regressions/index.test.js") is satisfied by the generic suite. The only unique value here is the guard that LetterAvatars still renders an "OP" avatar.

Failure scenario: two tests cover one criterion; a future change updates the generic suite's thresholds and leaves this copy behind, and the two drift apart.

Fix: remove the bespoke describe, or shrink it to the "OP avatar still exists" guard if that guard is worth keeping.

Tests (1)

2. ℹ️ Avatar demos assert only visual axe rules

The avatar rules omit assertions: 'all' (button and checkbox use it). An image-alt regression on AvatarA11yImage — the fixture built to exercise that rule — is only caught by the committed-JSON drift check, not by a direct assertion. That guard is real, but assertions: 'all' on the clean fixtures would fail closer to the cause.

Verdict

Approve after nits - correct enrolment and tests; the duplicate 1.4.12 check is worth removing.

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