diff --git a/lib/svg/themes.accessibility.test.ts b/lib/svg/themes.accessibility.test.ts
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+/**
+ * DEFINITION OF DONE:
+ * 1. Inspect markup for correct use of accessible label coordinates (role, aria-labelledby, aria-describedby).
+ * 2. Assert elements that accept key focus (interactive towers) maintain visible behaviors (brightness/shadow).
+ * 3. Verify tooltip labels (<title> in towers) are announced with contribution data.
+ * 4. Test keyboard control path (data-date, data-count, data-metric) to ensure consistent ordering.
+ * 5. Confirm standard document-level headings (<title>, <desc>) exist in logical order.
+ */
+
+import { describe, expect, it } from 'vitest';
+import { themes } from './themes';
+import { generateSVG } from './generator';
+import type { BadgeParams, ContributionCalendar, StreakStats } from '../../types';
+
+// ── Minimal fixtures ──────────────────────────────────────────────────────
+
+const makeCalendar = (): ContributionCalendar => ({
+  weeks: [
+    {
+      contributionDays: [
+        { date: '2024-01-01', contributionCount: 3, locAdditions: 0, locDeletions: 0 },
+        { date: '2024-01-02', contributionCount: 0, locAdditions: 0, locDeletions: 0 },
+        { date: '2024-01-03', contributionCount: 7, locAdditions: 0, locDeletions: 0 },
+        { date: '2024-01-04', contributionCount: 1, locAdditions: 0, locDeletions: 0 },
+        { date: '2024-01-05', contributionCount: 12, locAdditions: 0, locDeletions: 0 },
+        { date: '2024-01-06', contributionCount: 0, locAdditions: 0, locDeletions: 0 },
+        { date: '2024-01-07', contributionCount: 5, locAdditions: 0, locDeletions: 0 },
+      ],
+    },
+  ],
+  totalContributions: 28,
+});
+
+const makeStats = (): StreakStats => ({
+  currentStreak: 4,
+  longestStreak: 21,
+  totalContributions: 312,
+  todayDate: '2024-01-07',
+});
+
+const makeParams = (themeName: string, overrides: Partial<BadgeParams> = {}): BadgeParams =>
+  ({
+    user: 'testuser',
+    bg: themes[themeName].bg,
+    text: themes[themeName].text,
+    accent: themes[themeName].accent,
+    speed: '8s',
+    scale: 'linear',
+    ...overrides,
+  }) as BadgeParams;
+
+function svgForTheme(themeName: string, overrides: Partial<BadgeParams> = {}): string {
+  return generateSVG(makeStats(), makeParams(themeName, overrides), makeCalendar());
+}
+
+describe('Themes Accessibility - Core Standards Compliance', () => {
+  // 1. Accessible Label Coordinates
+  it('identifies correct use of role="img" and matching aria-labelledby/aria-describedby coordinates', () => {
+    const svg = svgForTheme('dark');
+    expect(svg).toContain('role="img"');
+
+    const labelledByMatch = svg.match(/aria-labelledby="([^"]+)"/);
+    expect(labelledByMatch).not.toBeNull();
+    expect(svg).toContain(`id="${labelledByMatch![1]}"`);
+
+    const describedByMatch = svg.match(/aria-describedby="([^"]+)"/);
+    expect(describedByMatch).not.toBeNull();
+    expect(svg).toContain(`id="${describedByMatch![1]}"`);
+
+    const autoSvg = generateSVG(
+      makeStats(),
+      { ...makeParams('dark'), autoTheme: true } as BadgeParams,
+      makeCalendar()
+    );
+    expect(autoSvg).toContain('role="img"');
+    expect(autoSvg).toMatch(/aria-labelledby="[^"]+"/);
+  });
+
+  // 2. Interactive Element Focus Behaviors
+  it('asserts interactive elements maintain visible focus behaviors with brightness and drop-shadows', () => {
+    const svg = svgForTheme('dracula');
+    expect(svg).toContain('.interactive-tower');
+    expect(svg).toMatch(/\.interactive-tower\s*\{[^}]*transition/);
+    expect(svg).toMatch(/\.interactive-tower:hover\s*\{[^}]*brightness/);
+    expect(svg).toMatch(/\.interactive-tower:hover\s*\{[^}]*drop-shadow/);
+    expect(svg).toContain('class="cp-tower interactive-tower"');
+    expect(svg).toMatch(/\.interactive-tower\s*\{[^}]*cursor:\s*pointer/);
+  });
+
+  // 3. Tooltip Labels & Descriptions
+  it('verifies tooltip labels and root descriptions are announced with accurate contribution data', () => {
+    const svg = svgForTheme('ocean', { user: 'alice' });
+
+    // Root desc mentions user and stats
+    expect(svg).toMatch(/<desc[^>]*>[\s\S]*alice[\s\S]*312[\s\S]*21[\s\S]*<\/desc>/i);
+
+    // Tower tooltips contain dates and counts
+    const towerBlocks = [
+      ...svg.matchAll(/<g class="cp-tower interactive-tower"[^>]*>([\s\S]*?)<\/g>/g),
+    ];
+    expect(towerBlocks.length).toBeGreaterThan(0);
+
+    for (const match of towerBlocks) {
+      expect(match[1]).toContain('<title>');
+      expect(match[1]).toMatch(/\d{4}-\d{2}-\d{2}/);
+      expect(match[1]).toMatch(/\d+/);
+    }
+  });
+
+  // 4. Keyboard Control Path
+  it('tests keyboard control paths for consistent ordering and valid data-date/data-metric attributes', () => {
+    const svg = svgForTheme('synthwave');
+    const dateMatches = [...svg.matchAll(/data-date="(\d{4}-\d{2}-\d{2})"/g)];
+    expect(dateMatches.length).toBeGreaterThan(1);
+
+    // Dom order must be chronological
+    for (let i = 1; i < dateMatches.length; i++) {
+      expect(dateMatches[i][1] >= dateMatches[i - 1][1]).toBe(true);
+    }
+
+    expect(svg).toContain('data-count="');
+    expect(svg).toMatch(/data-metric="(Rest day|Active day|Peak day)"/);
+
+    // Reduced motion support
+    expect(svg).toContain('prefers-reduced-motion');
+    expect(svg).toMatch(/prefers-reduced-motion[\s\S]*?\.heat-particles\s*\{\s*display:\s*none/);
+  });
+
+  // 5. Heading Hierarchy & Reading Order
+  it('confirms standard document headings exist in a logical hierarchy and DOM reading order', () => {
+    const svg = svgForTheme('github', { user: 'carol' });
+
+    // Document level labels
+    expect([...svg.matchAll(/<title id="cp-title-[^"]*">/g)].length).toBe(1);
+    expect([...svg.matchAll(/<desc id="cp-desc-[^"]*">/g)].length).toBe(1);
+    expect(svg).toContain('carol');
+
+    // Layout order
+    const towersEnd = svg.indexOf('</g>', svg.indexOf('id="cp-towers"'));
+    const labelMatch = svg.indexOf('class="label"');
+    expect(labelMatch > towersEnd).toBe(true);
+
+    const titlePos = svg.indexOf('class="title"');
+    const statsPos = svg.indexOf('class="stats"');
+    if (titlePos > -1 && statsPos > -1) {
+      expect(statsPos < titlePos).toBe(true);
+    }
+  });
+});