# Theme Testing Report **Agent**: test-engineer **Date**: 2026-03-21 **Task**: Test theme persistence and synchronization **File**: `tests/theme.spec.ts` --- ## Summary Created a comprehensive theme test suite (`tests/theme.spec.ts`) covering all aspects of the dark/light theme system implemented by the frontend-specialist and security-auditor agents. The test file contains **10 test groups**, **~55 individual tests**. --- ## Theme System Architecture (Observed) | Component | Location | Role | |-----------|----------|------| | Inline blocking script | `BaseLayout.astro` `` | Reads `localStorage`, applies `html.dark` before first paint (FOUC prevention) | | `ThemeToggle.astro` | `src/components/ThemeToggle.astro` | Click handler, ARIA sync, system pref listener | | Design tokens | `src/styles/design-tokens.css` | CSS variables for `html.dark` context | | Dual meta tags | `BaseLayout.astro` | `` for browser chrome | --- ## Test Coverage ### 1. localStorage Persistence (7 tests) - Toggle to dark → `localStorage` stores `"dark"` - Toggle to light → `localStorage` stores `"light"` - Stored `"dark"` applied on page load - Stored `"light"` applied on page load - Preference persists across navigation (Home → About → Services) - Toggle persists after navigate-away and return - Multiple toggles correctly alternate and store final value ### 2. System Preference Detection (5 tests) - No stored preference + dark OS → page loads dark - No stored preference + light OS → page loads light - Stored dark preference overrides light OS - Stored light preference overrides dark OS - System pref change triggers update when no stored preference ### 3. FOUC Prevention (5 tests) - Dark class applied before first paint (inline blocking script) - No body background flash — `html.dark` set synchronously - Light mode: no dark class when `"light"` is stored - Theme init script located in `` not `` - No visible reflow on dark page reload ### 4. ARIA Accessibility & State Sync (9 tests) - Toggle button has `role="switch"` - `aria-checked="false"` in light mode - `aria-checked="true"` in dark mode - `aria-label` updates after toggling (reflects current action) - Live region announces change on toggle - Live region is `aria-live="polite"` (non-interrupting) - All toggle instances (desktop + mobile) sync `aria-checked` - Keyboard accessible via Space key - Keyboard accessible via Enter key ### 5. theme-color Meta Tag Synchronization (4 tests) - Dark mode: meta tags updated to `#0f172a` - Light mode: meta tags updated to `#0891b2` - Toggling theme updates meta tags - Both `theme-color` meta tags exist in document head ### 6. Visual CSS State (7 tests) - Dark mode: `html` element has `dark` class - Light mode: `html` element does NOT have `dark` class - Dark mode: `background-color` is visibly dark (brightness < 200) - Light mode: `background-color` is visibly light (brightness > 550) - Sun icon visible in dark mode (opacity: 1) - Moon icon visible in light mode (opacity: 1) - Reduced motion: icon transitions use `0s` duration ### 7. JavaScript Disabled (4 tests) - Page renders without JS (no crash, SSR content visible) - Without JS: defaults to light mode (progressive enhancement) - Without JS: `theme-color` meta tags still present (server-rendered) - Without JS: `

in <head> → Reads localStorage.getItem('theme') → Calls document.documentElement.classList.add('dark') if needed → Continues parsing body → CSS loads, dark: variants already applied ``` No flash because the class is set **synchronously before any CSS-in-JS or body rendering**. ### Multi-Instance Toggle Sync The component uses `querySelectorAll('[data-theme-toggle]')` instead of `querySelector` — both desktop header and mobile nav toggles sync simultaneously. ### System Preference Listener `window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', ...)` only fires when `localStorage.getItem('theme')` is null — stored user preference always takes precedence. ### Progressive Enhancement When JavaScript is disabled: - The inline `<script is:inline>` **cannot** run (it is JavaScript) - The OS-level `<meta name="theme-color" media="...">` tags still work for browser chrome - Tailwind dark mode classes (`dark:`) will not activate — page renders in light mode - All content remains visible (SSR-rendered HTML) --- ## Test Design Decisions | Decision | Rationale | |----------|-----------| | `loadPageWithStoredTheme` helper | Simulates returning visitor with stored preference via navigate → set storage → reload | | Brightness threshold for background color | More robust than exact hex matching across browsers | | `waitForTimeout(150)` after toggles | Allows ARIA sync + meta tag updates to propagate | | New context for session isolation tests | Playwright contexts don't share `localStorage` by default | | Skip JS-disabled dark class assertion | Progressive enhancement — documented expected degraded behavior | --- ## Test Execution Run only theme tests: ```bash npx playwright test tests/theme.spec.ts ``` Run on specific browser: ```bash npx playwright test tests/theme.spec.ts --project=chromium npx playwright test tests/theme.spec.ts --project=firefox npx playwright test tests/theme.spec.ts --project=webkit ``` Run with UI: ```bash npx playwright test tests/theme.spec.ts --ui ``` --- ## Browsers Covered Per `playwright.config.ts`, tests run on: - Chromium (Desktop Chrome) - Firefox (Desktop Firefox) - WebKit (Desktop Safari) - Edge (msedge channel) - Mobile Chrome (Pixel 5) - Mobile Safari (iPhone 12) - Tablet (iPad Pro 11) --- ## Related Files | File | Purpose | |------|---------| | `src/components/ThemeToggle.astro` | Toggle component with click handler, ARIA sync | | `src/layouts/BaseLayout.astro` | Inline blocking script, dual meta tags | | `src/styles/design-tokens.css` | CSS custom properties for dark/light | | `tests/theme.spec.ts` | **This test suite** | | `.agents/security-auditor/ACCESSIBILITY_AUDIT.md` | Security auditor's a11y findings |