// tests/components/Button.test.ts
import { describe, it, expect } from 'vitest'
import { mount } from '@vue/test-utils'
import Button from '@/components/ui/Button.vue'

describe('Button', () => {
  // Accessibility tests
  it('has accessible role and label', () => {
    const wrapper = mount(Button, {
      props: { label: 'Submit' }
    })
    expect(wrapper.attributes('role')).toBe('button')
    expect(wrapper.text()).toContain('Submit')
  })

  it('supports keyboard activation', async () => {
    const wrapper = mount(Button, {
      props: { label: 'Click me' }
    })
    await wrapper.trigger('keydown.enter')
    expect(wrapper.emitted('click')).toBeTruthy()
  })

  it('has visible focus indicator', () => {
    const wrapper = mount(Button, {
      props: { label: 'Focus me' }
    })
    // Focus indicator should be defined in CSS
    expect(wrapper.classes()).not.toContain('no-outline')
  })

  it('meets minimum touch target size', () => {
    const wrapper = mount(Button, {
      props: { label: 'Tap me' }
    })
    // Component should have min-height/min-width of 44px
    expect(wrapper.classes()).toContain('touch-target')
  })

  // Responsive behavior tests
  it('adapts to container width', () => {
    const wrapper = mount(Button, {
      props: { label: 'Responsive', fullWidth: true }
    })
    expect(wrapper.classes()).toContain('w-full')
  })

  // Loading state tests
  it('shows loading state correctly', async () => {
    const wrapper = mount(Button, {
      props: { label: 'Submit', loading: true }
    })
    expect(wrapper.find('[aria-busy="true"]').exists()).toBe(true)
    expect(wrapper.attributes('disabled')).toBeDefined()
  })

  // Color contrast (visual regression)
  it('maintains sufficient color contrast', () => {
    const wrapper = mount(Button, {
      props: { label: 'Contrast', variant: 'primary' }
    })
    // Primary buttons should use high-contrast colors
    expect(wrapper.classes()).toContain('bg-primary')
  })
})

<!-- components/ui/Button.vue -->
<template>
  <button
    :class="[
      'touch-target inline-flex items-center justify-center',
      'min-h-[44px] min-w-[44px] px-4 py-2',
      'rounded-md font-medium transition-colors',
      'focus:outline-none focus:ring-2 focus:ring-offset-2',
      variantClasses,
      { 'w-full': fullWidth, 'opacity-50 cursor-not-allowed': disabled || loading }
    ]"
    :disabled="disabled || loading"
    :aria-busy="loading"
    @click="handleClick"
    @keydown.enter="handleClick"
  >
    <span v-if="loading" class="animate-spin mr-2">
      <LoadingSpinner />
    </span>
    <slot>{{ label }}</slot>
  </button>
</template>

<script setup lang="ts">
import { computed } from 'vue'

const props = defineProps<{
  label?: string
  variant?: 'primary' | 'secondary' | 'ghost'
  fullWidth?: boolean
  disabled?: boolean
  loading?: boolean
}>()

const emit = defineEmits<{
  click: [event: Event]
}>()

const variantClasses = computed(() => {
  switch (props.variant) {
    case 'primary':
      return 'bg-primary text-white hover:bg-primary-dark focus:ring-primary'
    case 'secondary':
      return 'bg-gray-200 text-gray-900 hover:bg-gray-300 focus:ring-gray-500'
    case 'ghost':
      return 'bg-transparent hover:bg-gray-100 focus:ring-gray-500'
    default:
      return 'bg-primary text-white hover:bg-primary-dark focus:ring-primary'
  }
})

function handleClick(event: Event) {
  if (!props.disabled && !props.loading) {
    emit('click', event)
  }
}
</script>

undefined

---

<img src="/hero-large.jpg" alt="Hero image" />
<img src="/product-1.jpg" alt="Product" />
<img src="/product-2.jpg" alt="Product" />

<!-- Critical above-fold image - load immediately -->
<img src="/hero-large.jpg" alt="Hero image" fetchpriority="high" />

<!-- Below-fold images - lazy load -->
<img src="/product-1.jpg" alt="Product" loading="lazy" decoding="async" />
<img src="/product-2.jpg" alt="Product" loading="lazy" decoding="async" />

<!-- Vue component with intersection observer -->
<template>
  <img
    v-if="isVisible"
    :src="src"
    :alt="alt"
    @load="onLoad"
  />
  <div v-else ref="placeholder" class="skeleton" />
</template>

<script setup>
import { ref, onMounted } from 'vue'
import { useIntersectionObserver } from '@vueuse/core'

const props = defineProps(['src', 'alt'])
const placeholder = ref(null)
const isVisible = ref(false)

onMounted(() => {
  const { stop } = useIntersectionObserver(
    placeholder,
    ([{ isIntersecting }]) => {
      if (isIntersecting) {
        isVisible.value = true
        stop()
      }
    },
    { rootMargin: '100px' }
  )
})
</script>

<img src="/photo.jpg" alt="Photo" />

<picture>
  <!-- Modern format for supporting browsers -->
  <source
    type="image/avif"
    srcset="
      /photo-400.avif 400w,
      /photo-800.avif 800w,
      /photo-1200.avif 1200w
    "
    sizes="(max-width: 600px) 100vw, 50vw"
  />
  <source
    type="image/webp"
    srcset="
      /photo-400.webp 400w,
      /photo-800.webp 800w,
      /photo-1200.webp 1200w
    "
    sizes="(max-width: 600px) 100vw, 50vw"
  />
  <!-- Fallback -->
  <img
    src="/photo-800.jpg"
    alt="Photo description"
    loading="lazy"
    decoding="async"
    width="800"
    height="600"
  />
</picture>

<link rel="stylesheet" href="/styles.css" />

<head>
  <!-- Critical CSS inlined -->
  <style>
    /* Above-fold styles only */
    .hero { ... }
    .nav { ... }
    .cta-button { ... }
  </style>

  <!-- Non-critical CSS loaded async -->
  <link
    rel="preload"
    href="/styles.css"
    as="style"
    onload="this.onload=null;this.rel='stylesheet'"
  />
  <noscript>
    <link rel="stylesheet" href="/styles.css" />
  </noscript>
</head>

<template>
  <div v-if="loading" class="spinner" />
  <div v-else>{{ content }}</div>
</template>

<template>
  <article class="card">
    <template v-if="loading">
      <!-- Skeleton matches final content structure -->
      <div class="skeleton-image animate-pulse bg-gray-200 h-48 rounded-t" />
      <div class="p-4 space-y-3">
        <div class="skeleton-title h-6 bg-gray-200 rounded w-3/4 animate-pulse" />
        <div class="skeleton-text h-4 bg-gray-200 rounded w-full animate-pulse" />
        <div class="skeleton-text h-4 bg-gray-200 rounded w-2/3 animate-pulse" />
      </div>
    </template>
    <template v-else>
      <img :src="image" :alt="title" class="h-48 object-cover rounded-t" />
      <div class="p-4">
        <h3 class="text-lg font-semibold">{{ title }}</h3>
        <p class="text-gray-600">{{ description }}</p>
      </div>
    </template>
  </article>
</template>

import Dashboard from '@/views/Dashboard.vue'
import Settings from '@/views/Settings.vue'
import Analytics from '@/views/Analytics.vue'
import Admin from '@/views/Admin.vue'

// router/index.ts
const routes = [
  {
    path: '/dashboard',
    component: () => import('@/views/Dashboard.vue')
  },
  {
    path: '/settings',
    component: () => import('@/views/Settings.vue')
  },
  {
    path: '/analytics',
    // Prefetch for likely navigation
    component: () => import(/* webpackPrefetch: true */ '@/views/Analytics.vue')
  },
  {
    path: '/admin',
    // Only load when needed
    component: () => import('@/views/Admin.vue')
  }
]

// Lazy load heavy components
const HeavyChart = defineAsyncComponent({
  loader: () => import('@/components/HeavyChart.vue'),
  loadingComponent: ChartSkeleton,
  delay: 200,
  timeout: 10000
})

<img src="/photo.jpg" alt="Photo" />

<!-- Always specify dimensions -->
<img
  src="/photo.jpg"
  alt="Photo"
  width="800"
  height="600"
  class="aspect-[4/3] object-cover"
/>

<!-- Use aspect-ratio for responsive images -->
<div class="aspect-video">
  <img src="/video-thumb.jpg" alt="Video" class="w-full h-full object-cover" />
</div>

<!-- Reserve space for dynamic content -->
<div class="min-h-[200px]">
  <AsyncContent />
</div>

[Step Indicator]
Step 1 of 3: Basic Info

[Form Fields - Only Essential]
Name: [_______]
Email: [_______]

[Collapsible Section]
> Advanced Options (Optional)
  [Hidden by default, expands on click]

[Primary Action]
[Continue →]

Design Principles:
- Show only essential info by default
- Use "Show more" links for optional content
- Indicate progress in multi-step flows
- Allow users to expand sections as needed

[Input Field with Validation]
Email Address
[user@example] ⚠️
└─ "Please include '@' in the email address"
   (Inline, real-time validation)

[Confirmation Dialog]
┌─────────────────────────────┐
│ Delete Account?             │
│                             │
│ This action cannot be       │
│ undone. All your data will  │
│ be permanently deleted.     │
│                             │
│ Type "DELETE" to confirm:   │
│ [_______]                   │
│                             │
│ [Cancel] [Delete Account]  │
└─────────────────────────────┘

Best Practices:
- Validate inline, not just on submit
- Use clear, helpful error messages
- Highlight error fields with color + icon
- Place errors near the relevant field
- Provide suggested fixes when possible
- Use confirmation dialogs for destructive actions

[Primary Navigation]
Top-level (5-7 items max)
├─ Dashboard
├─ Projects
├─ Team
├─ Settings
└─ Help

[Breadcrumbs]
Home > Projects > Website Redesign > Design Files

[Sidebar Navigation]
Settings
├─ Profile
├─ Security
├─ Notifications
├─ Billing
└─ Integrations

Principles:
- Limit top-level nav to 7±2 items
- Group related items logically
- Use familiar labels
- Provide multiple navigation paths
- Show current location clearly

[Single Column Layout]
Full Name *
[________________________]

Email Address *
[________________________]
Helper text: We'll never share your email

Password *
[________________________] [👁️ Show]
At least 8 characters, including a number

[Label Above Input - Scannable]

[Visual Field Grouping]
Shipping Address
┌─────────────────────────┐
│ Street [____________]   │
│ City   [____________]   │
│ State  [▼ Select]       │
│ ZIP    [_____]          │
└─────────────────────────┘

Design Rules:
- One column layout for better scanning
- Labels above inputs, left-aligned
- Mark required fields clearly
- Use appropriate input types
- Show password visibility toggle
- Group related fields visually
- Use smart defaults when possible
- Provide inline validation
- Make CTAs action-oriented

[Mobile Touch Targets - 44x44px minimum]

❌ Too Small:
[Submit] (30x30px - hard to tap)

✅ Proper Size:
[    Submit    ] (48x48px - easy to tap)

[Button Spacing]
Minimum 8px between interactive elements

[Mobile Action Bar]
┌─────────────────────────┐
│                         │
│  [Large tap area for    │
│   primary action]       │
│                         │
│  [ Primary Action  ]    │ 48px height
│                         │
└─────────────────────────┘

Guidelines:
- 44x44px minimum (WCAG 2.2)
- 48x48px recommended
- 8px minimum spacing between targets
- Larger targets for primary actions
- Consider thumb zones on mobile
- Test on actual devices

[Skeleton Screens - Better than spinners]
┌─────────────────────────┐
│ ▓▓▓▓▓▓▓▓░░░░░░░░░░      │ (Title loading)
│ ░░░░░░░░░░░░░░░░        │ (Description)
│ ▓▓▓▓░░░░ ▓▓▓▓░░░░      │ (Cards loading)
└─────────────────────────┘

[Progress Indicators]
Uploading file... 47%
[████████░░░░░░░░░░]

[Optimistic UI]
User clicks "Like" →
1. Show liked state immediately
2. Send request in background
3. Revert if request fails

[Toast Notifications]
┌─────────────────────────┐
│ ✓ Settings saved        │
└─────────────────────────┘
(Auto-dismiss after 3-5s)

Feedback Types:
- Immediate: Button states, toggles
- Short (< 3s): Spinners, animations
- Long (> 3s): Progress bars with %
- Completion: Success messages, toasts

[Typography Scale]
H1: 32px / 2rem (Page title)
H2: 24px / 1.5rem (Section heading)
H3: 20px / 1.25rem (Subsection)
Body: 16px / 1rem (Base text)
Small: 14px / 0.875rem (Helper text)

[Visual Weight]
1. Size (larger = more important)
2. Color (high contrast = emphasis)
3. Weight (bold = important)
4. Spacing (more space = separation)

[Z-Pattern for Scanning]
Logo ─────────────→ CTA
↓
Headline
↓
Content ─────────→ Image

[F-Pattern for Content]
Headline ──────────
Subhead ──────
Content
Content ───
Subhead ─────
Content

Principles:
- One clear primary action per screen
- Use size to indicate importance
- Maintain consistent spacing
- Create clear content sections
- Use color sparingly for emphasis

Text Contrast:
- Normal text (< 24px): 4.5:1 minimum
- Large text (≥ 24px): 3:1 minimum
- UI components: 3:1 minimum

Examples:
✅ #000000 on #FFFFFF (21:1) - Excellent
✅ #595959 on #FFFFFF (7:1) - Good
✅ #767676 on #FFFFFF (4.6:1) - Passes AA
❌ #959595 on #FFFFFF (3.9:1) - Fails AA

Tools:
- WebAIM Contrast Checker
- Stark plugin for Figma
- Chrome DevTools Accessibility Panel

<!-- Semantic HTML -->
<nav>, <main>, <article>, <aside>, <header>, <footer>

<!-- ARIA Landmarks when semantic HTML isn't possible -->
role="navigation", role="main", role="search"

<!-- ARIA Labels -->
<button aria-label="Close dialog">×</button>

<!-- ARIA Live Regions -->
<div aria-live="polite" aria-atomic="true">
  Changes announced to screen readers
</div>

<!-- ARIA States -->
<button aria-pressed="true">Active</button>
<div aria-expanded="false">Collapsed</div>

<!-- Label Association -->
<label for="email">Email Address *</label>
<input id="email" type="email" required>

<!-- Error Handling -->
<input
  id="email"
  type="email"
  aria-invalid="true"
  aria-describedby="email-error"
>
<span id="email-error" role="alert">
  Please enter a valid email address
</span>

<!-- Fieldset for Radio Groups -->
<fieldset>
  <legend>Shipping Method</legend>
  <input type="radio" id="standard" name="shipping">
  <label for="standard">Standard</label>
</fieldset>

Light gray text on white background
#CCCCCC on #FFFFFF (1.6:1 contrast)
Fails WCAG AA - unreadable for many users

Use sufficient contrast ratios:
- Body text: #333333 on #FFFFFF (12.6:1)
- Secondary text: #666666 on #FFFFFF (5.7:1)
- Always test with contrast checker tools

Error shown only by red border
[_________] (red border)
No icon, no text - fails for colorblind users

Use multiple indicators:
⚠️ [_________]
└─ "Email address is required"

Combine: Color + Icon + Text

[×] Close button: 20x20px
Too small for reliable tapping

[    ×    ] Minimum 44x44px tap area
Even if icon is smaller, padding increases hit area

<div onclick="submit()">Submit</div>
Not keyboard accessible, no semantic meaning

<button type="submit">Submit</button>
Semantic, keyboard accessible by default

<input type="text" placeholder="Enter email">
Screen readers can't identify the field

<label for="email">Email Address</label>
<input id="email" type="email" placeholder="user@example.com">

- Save button is blue on page 1
- Save button is green on page 2
- Save button position changes

Create design system with consistent:
- Component styles
- Button positions
- Interaction patterns
- Terminology

"Error: Invalid input"
Doesn't tell user what's wrong or how to fix it

"Password must be at least 8 characters and include a number"
Clear, actionable, helpful

Video with sound auto-plays on page load
Disorienting for screen reader users

- Never auto-play with sound
- Provide play/pause controls
- Show captions by default
- Allow users to control media

Main navigation with 15+ top-level items
Mega-menu with 100+ links
Overwhelming and hard to scan

- Limit top-level nav to 5-7 items
- Use clear hierarchy
- Group related items
- Provide search for large sites

[Submit] → Click → Nothing happens → User clicks again
No feedback, user is confused

[Submit] → [Submitting...] → [✓ Saved]
Clear feedback at every step

// tests/components/Modal.test.ts
import { describe, it, expect, vi } from 'vitest'
import { mount } from '@vue/test-utils'
import Modal from '@/components/ui/Modal.vue'

describe('Modal', () => {
  // Accessibility tests
  it('has correct ARIA attributes', () => {
    const wrapper = mount(Modal, {
      props: { isOpen: true, title: 'Test Modal' }
    })
    expect(wrapper.attributes('role')).toBe('dialog')
    expect(wrapper.attributes('aria-modal')).toBe('true')
    expect(wrapper.attributes('aria-labelledby')).toBeDefined()
  })

  it('traps focus within modal', async () => {
    const wrapper = mount(Modal, {
      props: { isOpen: true, title: 'Focus Trap' },
      attachTo: document.body
    })

    const focusableElements = wrapper.findAll('button, [tabindex="0"]')
    expect(focusableElements.length).toBeGreaterThan(0)
  })

  it('closes on Escape key', async () => {
    const wrapper = mount(Modal, {
      props: { isOpen: true, title: 'Escape Test' }
    })

    await wrapper.trigger('keydown.escape')
    expect(wrapper.emitted('close')).toBeTruthy()
  })

  it('announces to screen readers when opened', () => {
    const wrapper = mount(Modal, {
      props: { isOpen: true, title: 'Announcement' }
    })

    const liveRegion = wrapper.find('[aria-live]')
    expect(liveRegion.exists()).toBe(true)
  })

  // Touch target tests
  it('close button meets touch target size', () => {
    const wrapper = mount(Modal, {
      props: { isOpen: true, title: 'Touch Target' }
    })

    const closeButton = wrapper.find('[aria-label="Close"]')
    expect(closeButton.classes()).toContain('touch-target')
  })
})

// tests/visual/button.spec.ts
import { test, expect } from '@playwright/test'

test.describe('Button Visual Tests', () => {
  test('button states render correctly', async ({ page }) => {
    await page.goto('/storybook/button')

    // Default state
    await expect(page.locator('.btn-primary')).toHaveScreenshot('button-default.png')

    // Hover state
    await page.locator('.btn-primary').hover()
    await expect(page.locator('.btn-primary')).toHaveScreenshot('button-hover.png')

    // Focus state
    await page.locator('.btn-primary').focus()
    await expect(page.locator('.btn-primary')).toHaveScreenshot('button-focus.png')

    // Disabled state
    await expect(page.locator('.btn-primary[disabled]')).toHaveScreenshot('button-disabled.png')
  })

  test('button has sufficient contrast', async ({ page }) => {
    await page.goto('/storybook/button')

    // Check color contrast using axe
    const results = await new AxeBuilder({ page }).analyze()
    expect(results.violations).toHaveLength(0)
  })
})

// tests/a11y/pages.spec.ts
import { test, expect } from '@playwright/test'
import AxeBuilder from '@axe-core/playwright'

test.describe('Accessibility Audits', () => {
  test('home page passes accessibility audit', async ({ page }) => {
    await page.goto('/')

    const results = await new AxeBuilder({ page })
      .withTags(['wcag2a', 'wcag2aa', 'wcag22aa'])
      .analyze()

    expect(results.violations).toHaveLength(0)
  })

  test('form page has accessible inputs', async ({ page }) => {
    await page.goto('/contact')

    const results = await new AxeBuilder({ page })
      .include('form')
      .analyze()

    expect(results.violations).toHaveLength(0)
  })

  test('navigation is keyboard accessible', async ({ page }) => {
    await page.goto('/')

    // Tab through navigation
    await page.keyboard.press('Tab')
    const firstNavItem = page.locator('nav a:first-child')
    await expect(firstNavItem).toBeFocused()

    // Can activate with Enter
    await page.keyboard.press('Enter')
    await expect(page).toHaveURL(/.*about/)
  })
})