test: add Phase 3 audit fixture translating iframe-title peer cases

Translates 33 cases from peer-plugin rules:
  - jsx-a11y iframe-has-title
  - vuejs-accessibility iframe-has-title
  - lit-a11y iframe-title

Fixture documents parity after this fix:
  - title={{null|undefined|number}} and concat `title="{{null}}"`
    / `title="{{42}}"` are now flagged via dynamicFalseTitle.

Remaining divergences (title={{""}} still accepted, aria-hidden /
hidden exemption, whitespace-only title over-flagged, duplicate-title
detection inherited from ember-template-lint) are annotated inline.

Author: johanrd

tests/audit/iframe-title/peer-parity.js

@@ -0,0 +1,209 @@
+// Audit fixture — peer-plugin parity for `ember/template-require-iframe-title`.
+// These tests are NOT part of the main suite and do not run in CI. They encode
+// the CURRENT behavior of our rule so that running this file reports pass.
+// Each divergence from an upstream plugin is annotated as "DIVERGENCE —".
+//
+// Source files (context/ checkouts):
+//   - eslint-plugin-jsx-a11y-main/__tests__/src/rules/iframe-has-title-test.js
+//   - eslint-plugin-vuejs-accessibility-main/src/rules/__tests__/iframe-has-title.test.ts
+//   - eslint-plugin-lit-a11y/tests/lib/rules/iframe-title.js
+
+'use strict';
+
+const rule = require('../../../lib/rules/template-require-iframe-title');
+const RuleTester = require('eslint').RuleTester;
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+ruleTester.run('audit:iframe-title (gts)', rule, {
+  valid: [
+    // === Upstream parity — basic cases ===
+    // jsx-a11y / vue-a11y / lit-a11y: valid (no iframe, or titled iframe).
+    '<template><div /></template>',
+    '<template><iframe title="Unique title" /></template>',
+
+    // Dynamic title — jsx-a11y treats `title={foo}` as valid (expression is
+    // assumed to yield a truthy string). vue-a11y: valid for `:title="foo"`.
+    // lit-a11y: valid for `title=${foo}`. Ours: valid for `{{someValue}}`.
+    '<template><iframe title={{someValue}} /></template>',
+
+    // Ours: valid for concat-mustache (dynamic in concat).
+    // No direct jsx-a11y analogue because JSX has no string-interpolation; but
+    // the equivalent `title={`${foo}`}` is treated as valid by jsx-a11y.
+    '<template><iframe title="{{someValue}}" /></template>',
+
+    // === OUR behavior (no upstream peer equivalent) — exemptions ===
+    // Our rule skips iframes that are aria-hidden or hidden.
+    //   - jsx-a11y: does NOT exempt aria-hidden; `<iframe aria-hidden />`
+    //     without a title is still flagged.
+    //   - vue-a11y / lit-a11y: same — no aria-hidden/hidden exemption.
+    // Intentional: matches ember-template-lint upstream behavior.
+    '<template><iframe aria-hidden="true" /></template>',
+    '<template><iframe hidden /></template>',
+    '<template><iframe title="" aria-hidden /></template>',
+    '<template><iframe title="" hidden /></template>',
+
+    // === Remaining divergence — `title={{""}}` ===
+    // jsx-a11y flags `<iframe title={""} />` via getLiteralPropValue.
+    // Our rule inspects only GlimmerBooleanLiteral / GlimmerNullLiteral /
+    //   GlimmerUndefinedLiteral / GlimmerNumberLiteral — an empty-string
+    //   literal inside `{{}}` is not a GlimmerStringLiteral AST node but
+    //   a concat-of-nothing; we under-flag here.
+    '<template><iframe title={{""}} /></template>',
+
+    // === Disambiguation — distinct titles across iframes (all valid) ===
+    '<template><iframe title="foo" /><iframe title="bar" /></template>',
+  ],
+
+  invalid: [
+    // === Upstream parity — missing title ===
+    {
+      code: '<template><iframe /></template>',
+      output: null,
+      errors: [{ messageId: 'missingTitle' }],
+    },
+    {
+      code: '<template><iframe src="/content"></iframe></template>',
+      output: null,
+      errors: [{ messageId: 'missingTitle' }],
+    },
+
+    // === Upstream parity — empty title string ===
+    // jsx-a11y, vue-a11y, lit-a11y all flag `title=""`.
+    {
+      code: '<template><iframe title="" /></template>',
+      output: null,
+      errors: [{ messageId: 'emptyTitle' }],
+    },
+    // Whitespace-only title — ours trims then flags empty.
+    // jsx-a11y: `getLiteralPropValue("   ")` yields "   " which is truthy, so
+    // jsx-a11y would NOT flag. vue-a11y similarly does not trim. Ours trims.
+    // DIVERGENCE — we over-flag whitespace-only titles.
+    {
+      code: '<template><iframe title="   " /></template>',
+      output: null,
+      errors: [{ messageId: 'emptyTitle' }],
+    },
+
+    // === Parity — title is literal boolean / null / undefined / number ===
+    // jsx-a11y: INVALID for any non-string literal (via getLiteralPropValue
+    //   truthiness + string-check). vue-a11y: same. Our rule now rejects
+    //   GlimmerBooleanLiteral / GlimmerNullLiteral / GlimmerUndefinedLiteral
+    //   / GlimmerNumberLiteral in both `{{}}` and `"{{}}"` positions.
+    {
+      code: '<template><iframe title={{false}} /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<template><iframe title={{true}} /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<template><iframe title={{null}} /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<template><iframe title={{undefined}} /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<template><iframe title={{42}} /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    // Concat form — `title="{{false}}"` / etc. also flagged.
+    {
+      code: '<template><iframe title="{{false}}" /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<template><iframe title="{{null}}" /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<template><iframe title="{{42}}" /></template>',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+
+    // === DIVERGENCE — duplicate-title detection ===
+    // jsx-a11y, vue-a11y, lit-a11y: do NOT check for duplicate titles across
+    // multiple iframes. Our rule does (inherited from ember-template-lint).
+    // Captured here as one of our OVER-flagging cases (intentional extension).
+    {
+      code: '<template><iframe title="foo" /><iframe title="foo" /></template>',
+      output: null,
+      errors: [
+        { message: 'This title is not unique. #1' },
+        {
+          message:
+            '<iframe> elements must have a unique title property. Value title="foo" already used for different iframe. #1',
+        },
+      ],
+    },
+  ],
+});
+
+const hbsRuleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser/hbs'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+hbsRuleTester.run('audit:iframe-title (hbs)', rule, {
+  valid: [
+    '<iframe title="Welcome" />',
+    '<iframe title={{someValue}} />',
+    // DIVERGENCE — exempted (see gts section)
+    '<iframe aria-hidden="true" />',
+    '<iframe hidden />',
+  ],
+  invalid: [
+    {
+      code: '<iframe />',
+      output: null,
+      errors: [{ messageId: 'missingTitle' }],
+    },
+    {
+      code: '<iframe title="" />',
+      output: null,
+      errors: [{ messageId: 'emptyTitle' }],
+    },
+    // Parity — non-string literal titles.
+    {
+      code: '<iframe title={{false}} />',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<iframe title={{undefined}} />',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    {
+      code: '<iframe title={{42}} />',
+      output: null,
+      errors: [{ messageId: 'dynamicFalseTitle' }],
+    },
+    // DIVERGENCE — duplicate detection (upstream does not check).
+    {
+      code: '<iframe title="foo" /><iframe title="foo" />',
+      output: null,
+      errors: [
+        { message: 'This title is not unique. #1' },
+        {
+          message:
+            '<iframe> elements must have a unique title property. Value title="foo" already used for different iframe. #1',
+        },
+      ],
+    },
+  ],
+});