diff --git a/tests/projects-born-render.test.mjs b/tests/projects-born-render.test.mjs
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+++ b/tests/projects-born-render.test.mjs
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+// src/components/ProjectsBorn/index.js renders two visually different things
+// from one component: the full section embedded by docs/community/index.md and
+// docs/practitioners/index.md, and the `compact` strip that src/theme/Footer
+// puts on *every* page of the site.
+//
+// Only the full form had ever been executed, and only incidentally — as a
+// fixture inside tests/jsx-hooks.test.mjs, which asserts that the `@site` alias
+// resolves and nothing about the markup. The compact form was never rendered at
+// all, so the four `compact`-gated branches (the `aria-labelledby` id, the
+// intro paragraph, the per-project description and the TAB footer note) could
+// regress on every page without a single test noticing.
+//
+// tests/footer.test.mjs checks that the footer passes `compact`; it stops at
+// the unrendered element. These assertions cover what that flag actually does.
+
+import assert from 'node:assert/strict';
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import test from 'node:test';
+
+import { importSource } from './helpers-jsx.mjs';
+import {
+  findAllByType,
+  findByType,
+  textOf,
+  walkElements,
+} from './tools/react-element-tree.mjs';
+
+const { default: ProjectsBorn } = await importSource(
+  'src/components/ProjectsBorn/index.js',
+);
+
+// The component imports the corpus through the `@site` alias at module scope,
+// so the test has to assert against the same checked-in file rather than an
+// injected fixture.
+const projects = JSON.parse(
+  readFileSync(
+    fileURLToPath(new URL('../data/projects-born.json', import.meta.url)),
+    'utf8',
+  ),
+);
+
+const DEFAULT_TITLE = 'Projects born at end-user organizations';
+
+function anchorsOf(tree) {
+  return findAllByType(tree, 'a').filter((node) => node.props?.href);
+}
+
+function projectAnchors(tree) {
+  const urls = new Set(projects.map((project) => project.url));
+  return anchorsOf(tree).filter((node) => urls.has(node.props.href));
+}
+
+test('the full form renders one anchor per project in corpus order', () => {
+  const anchors = projectAnchors(ProjectsBorn({}));
+  assert.equal(anchors.length, projects.length);
+  assert.deepEqual(
+    anchors.map((node) => node.props.href),
+    projects.map((project) => project.url),
+  );
+});
+
+test('every project tile is keyed, so React can reorder the list', () => {
+  for (const anchor of projectAnchors(ProjectsBorn({}))) {
+    assert.ok(anchor.key, 'expected a stable key on each project tile');
+  }
+});
+
+test('each project contributes its name and origin to the rendered text', () => {
+  const text = textOf(ProjectsBorn({}));
+  for (const project of projects) {
+    assert.match(text, new RegExp(escape(project.name)));
+    assert.match(text, new RegExp(`Born at ${escape(project.origin)}`));
+  }
+});
+
+test('the full form carries the default title, intro and TAB footer note', () => {
+  const text = textOf(ProjectsBorn({}));
+  assert.match(text, new RegExp(escape(DEFAULT_TITLE)));
+  assert.match(text, /Some of the most widely adopted CNCF projects/);
+  assert.match(text, /Talk to the End User TAB/);
+});
+
+test('the full form prints every project description', () => {
+  const text = textOf(ProjectsBorn({}));
+  for (const project of projects) {
+    assert.match(text, new RegExp(escape(project.description)));
+  }
+});
+
+test('the compact strip drops the intro, descriptions and TAB footer note', () => {
+  // This is the form src/theme/Footer ships on every page: the same project
+  // list, stripped of the three prose blocks that belong on the page itself.
+  const text = textOf(ProjectsBorn({ compact: true }));
+  assert.doesNotMatch(text, /Some of the most widely adopted CNCF projects/);
+  assert.doesNotMatch(text, /Talk to the End User TAB/);
+  for (const project of projects) {
+    assert.doesNotMatch(text, new RegExp(escape(project.description)));
+  }
+});
+
+test('the compact strip still links every project by name and origin', () => {
+  const tree = ProjectsBorn({ compact: true });
+  const anchors = projectAnchors(tree);
+  assert.equal(anchors.length, projects.length);
+  const text = textOf(tree);
+  for (const project of projects) {
+    assert.match(text, new RegExp(escape(project.name)));
+    assert.match(text, new RegExp(`Born at ${escape(project.origin)}`));
+  }
+});
+
+test('the two forms label their headings with distinct ids', () => {
+  // Footer and page render simultaneously on a docs page that embeds the full
+  // section. A shared id would put two elements with the same id in one
+  // document and make `aria-labelledby` ambiguous for a screen reader.
+  const sectionId = headingIdOf(ProjectsBorn({}));
+  const footerId = headingIdOf(ProjectsBorn({ compact: true }));
+  assert.equal(sectionId, 'projects-born-title-section');
+  assert.equal(footerId, 'projects-born-title-footer');
+  assert.notEqual(sectionId, footerId);
+});
+
+test('each form points aria-labelledby at a heading that exists in its own tree', () => {
+  for (const props of [{}, { compact: true }]) {
+    const tree = ProjectsBorn(props);
+    assert.equal(tree.type, 'section');
+    const labelledBy = tree.props['aria-labelledby'];
+    assert.ok(labelledBy, 'expected the section to be labelled');
+    const heading = findByType(tree, 'h2');
+    assert.ok(heading, 'expected an h2 inside the section');
+    assert.equal(heading.props.id, labelledBy);
+  }
+});
+
+test('the title and intro props override the defaults', () => {
+  // docs/practitioners/index.md renders the section with its own copy.
+  const tree = ProjectsBorn({
+    title: 'Built in production, donated to CNCF',
+    intro: 'A practitioner-facing framing of the same corpus.',
+  });
+  const text = textOf(tree);
+  assert.match(text, /Built in production, donated to CNCF/);
+  assert.match(text, /A practitioner-facing framing of the same corpus\./);
+  assert.doesNotMatch(text, new RegExp(escape(DEFAULT_TITLE)));
+});
+
+test('the intro prop is ignored in the compact strip', () => {
+  const text = textOf(
+    ProjectsBorn({ compact: true, intro: 'SHOULD-NOT-RENDER' }),
+  );
+  assert.doesNotMatch(text, /SHOULD-NOT-RENDER/);
+});
+
+test('the decorative arrow is hidden from assistive technology', () => {
+  for (const props of [{}, { compact: true }]) {
+    const arrows = [...walkElements(ProjectsBorn(props))].filter(
+      (node) => textOf(node) === '↗',
+    );
+    assert.equal(arrows.length, projects.length);
+    for (const arrow of arrows) {
+      assert.equal(arrow.props['aria-hidden'], 'true');
+    }
+  }
+});
+
+test('no project tile opens a new tab without noreferrer', () => {
+  // The tiles are same-tab links today. If one ever gains target="_blank" it
+  // must not hand the destination a live window.opener handle.
+  for (const props of [{}, { compact: true }]) {
+    for (const anchor of anchorsOf(ProjectsBorn(props))) {
+      if (anchor.props.target === '_blank') {
+        assert.match(anchor.props.rel ?? '', /\bnoreferrer\b/);
+      }
+    }
+  }
+});
+
+function headingIdOf(tree) {
+  return findByType(tree, 'h2')?.props?.id;
+}
+
+function escape(value) {
+  return String(value).replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+}