screen-reader-testing（屏幕阅读器测试）

Screen Reader Testing

Practical guide to testing web applications with screen readers for comprehensive accessibility validation.

When to Use This Skill

• Validating screen reader compatibility
• Testing ARIA implementations
• Debugging assistive technology issues
• Verifying form accessibility
• Testing dynamic content announcements
• Ensuring navigation accessibility

Core Concepts

1. Major Screen Readers

2. Testing Priority

Minimum Coverage:
1. NVDA + Firefox (Windows)
2. VoiceOver + Safari (macOS)
3. VoiceOver + Safari (iOS)

Comprehensive Coverage:
+ JAWS + Chrome (Windows)
+ TalkBack + Chrome (Android)
+ Narrator + Edge (Windows)

3. Screen Reader Modes

VoiceOver (macOS)

Setup

Enable: System Preferences → Accessibility → VoiceOver
Toggle: Cmd + F5
Quick Toggle: Triple-press Touch ID

Essential Commands

Navigation:
VO = Ctrl + Option (VoiceOver modifier)

VO + Right Arrow   Next element
VO + Left Arrow    Previous element
VO + Shift + Down  Enter group
VO + Shift + Up    Exit group

Reading:
VO + A             Read all from cursor
Ctrl               Stop speaking
VO + B             Read current paragraph

Interaction:
VO + Space         Activate element
VO + Shift + M     Open menu
Tab                Next focusable element
Shift + Tab        Previous focusable element

Rotor (VO + U):
Navigate by: Headings, Links, Forms, Landmarks
Left/Right Arrow   Change rotor category
Up/Down Arrow      Navigate within category
Enter              Go to item

Web Specific:
VO + Cmd + H       Next heading
VO + Cmd + J       Next form control
VO + Cmd + L       Next link
VO + Cmd + T       Next table

Testing Checklist

## VoiceOver Testing Checklist

### Page Load

- [ ] Page title announced
- [ ] Main landmark found
- [ ] Skip link works

### Navigation

- [ ] All headings discoverable via rotor
- [ ] Heading levels logical (H1 → H2 → H3)
- [ ] Landmarks properly labeled
- [ ] Skip links functional

### Links & Buttons

- [ ] Link purpose clear
- [ ] Button actions described
- [ ] New window/tab announced

### Forms

- [ ] All labels read with inputs
- [ ] Required fields announced
- [ ] Error messages read
- [ ] Instructions available
- [ ] Focus moves to errors

### Dynamic Content

- [ ] Alerts announced immediately
- [ ] Loading states communicated
- [ ] Content updates announced
- [ ] Modals trap focus correctly

### Tables

- [ ] Headers associated with cells
- [ ] Table navigation works
- [ ] Complex tables have captions

Common Issues & Fixes

<!-- Issue: Button not announcing purpose -->
<button><svg>...</svg></button>

<!-- Fix -->
<button aria-label="Close dialog"><svg aria-hidden="true">...</svg></button>

<!-- Issue: Dynamic content not announced -->
<div id="results">New results loaded</div>

<!-- Fix -->
<div id="results" role="status" aria-live="polite">New results loaded</div>

<!-- Issue: Form error not read -->
<input type="email" />
<span class="error">Invalid email</span>

<!-- Fix -->
<input type="email" aria-invalid="true" aria-describedby="email-error" />
<span id="email-error" role="alert">Invalid email</span>

NVDA (Windows)

Setup

Download: nvaccess.org
Start: Ctrl + Alt + N
Stop: Insert + Q

Essential Commands

Navigation:
Insert = NVDA modifier

Down Arrow         Next line
Up Arrow           Previous line
Tab                Next focusable
Shift + Tab        Previous focusable

Reading:
NVDA + Down Arrow  Say all
Ctrl               Stop speech
NVDA + Up Arrow    Current line

Headings:
H                  Next heading
Shift + H          Previous heading
1-6                Heading level 1-6

Forms:
F                  Next form field
B                  Next button
E                  Next edit field
X                  Next checkbox
C                  Next combo box

Links:
K                  Next link
U                  Next unvisited link
V                  Next visited link

Landmarks:
D                  Next landmark
Shift + D          Previous landmark

Tables:
T                  Next table
Ctrl + Alt + Arrows Navigate cells

Elements List (NVDA + F7):
Shows all links, headings, form fields, landmarks

Browse vs Focus Mode

NVDA automatically switches modes:
- Browse Mode: Arrow keys navigate content
- Focus Mode: Arrow keys control interactive elements

Manual switch: NVDA + Space

Watch for:
- "Browse mode" announcement when navigating
- "Focus mode" when entering form fields
- Application role forces forms mode

Testing Script

## NVDA Test Script

### Initial Load

1. Navigate to page
2. Let page finish loading
3. Press Insert + Down to read all
4. Note: Page title, main content identified?

### Landmark Navigation

1. Press D repeatedly
2. Check: All main areas reachable?
3. Check: Landmarks properly labeled?

### Heading Navigation

1. Press Insert + F7 → Headings
2. Check: Logical heading structure?
3. Press H to navigate headings
4. Check: All sections discoverable?

### Form Testing

1. Press F to find first form field
2. Check: Label read?
3. Fill in invalid data
4. Submit form
5. Check: Errors announced?
6. Check: Focus moved to error?

### Interactive Elements

1. Tab through all interactive elements
2. Check: Each announces role and state
3. Activate buttons with Enter/Space
4. Check: Result announced?

### Dynamic Content

1. Trigger content update
2. Check: Change announced?
3. Open modal
4. Check: Focus trapped?
5. Close modal
6. Check: Focus returns?

JAWS (Windows)

Essential Commands

Start: Desktop shortcut or Ctrl + Alt + J
Virtual Cursor: Auto-enabled in browsers

Navigation:
Arrow keys         Navigate content
Tab                Next focusable
Insert + Down      Read all
Ctrl               Stop speech

Quick Keys:
H                  Next heading
T                  Next table
F                  Next form field
B                  Next button
G                  Next graphic
L                  Next list
;                  Next landmark

Forms Mode:
Enter              Enter forms mode
Numpad +           Exit forms mode
F5                 List form fields

Lists:
Insert + F7        Link list
Insert + F6        Heading list
Insert + F5        Form field list

Tables:
Ctrl + Alt + Arrows Table navigation

TalkBack (Android)

Setup

Enable: Settings → Accessibility → TalkBack
Toggle: Hold both volume buttons 3 seconds

Gestures

Explore: Drag finger across screen
Next: Swipe right
Previous: Swipe left
Activate: Double tap
Scroll: Two finger swipe

Reading Controls (swipe up then right):
- Headings
- Links
- Controls
- Characters
- Words
- Lines
- Paragraphs

Common Test Scenarios

1. Modal Dialog

<!-- Accessible modal structure -->
<div
  role="dialog"
  aria-modal="true"
  aria-labelledby="dialog-title"
  aria-describedby="dialog-desc"
>
  <h2 id="dialog-title">Confirm Delete</h2>
  <p id="dialog-desc">This action cannot be undone.</p>
  <button>Cancel</button>
  <button>Delete</button>
</div>

// Focus management
function openModal(modal) {
  // Store last focused element
  lastFocus = document.activeElement;

  // Move focus to modal
  modal.querySelector("h2").focus();

  // Trap focus
  modal.addEventListener("keydown", trapFocus);
}

function closeModal(modal) {
  // Return focus
  lastFocus.focus();
}

function trapFocus(e) {
  if (e.key === "Tab") {
    const focusable = modal.querySelectorAll(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])',
    );
    const first = focusable[0];
    const last = focusable[focusable.length - 1];

    if (e.shiftKey && document.activeElement === first) {
      last.focus();
      e.preventDefault();
    } else if (!e.shiftKey && document.activeElement === last) {
      first.focus();
      e.preventDefault();
    }
  }

  if (e.key === "Escape") {
    closeModal(modal);
  }
}

2. Live Regions

<!-- Status messages (polite) -->
<div role="status" aria-live="polite" aria-atomic="true">
  <!-- Content updates will be announced after current speech -->
</div>

<!-- Alerts (assertive) -->
<div role="alert" aria-live="assertive">
  <!-- Content updates interrupt current speech -->
</div>

<!-- Progress updates -->
<div
  role="progressbar"
  aria-valuenow="75"
  aria-valuemin="0"
  aria-valuemax="100"
  aria-label="Upload progress"
></div>

<!-- Log (additions only) -->
<div role="log" aria-live="polite" aria-relevant="additions">
  <!-- New messages announced, removals not -->
</div>

3. Tab Interface

<div role="tablist" aria-label="Product information">
  <button role="tab" id="tab-1" aria-selected="true" aria-controls="panel-1">
    Description
  </button>
  <button
    role="tab"
    id="tab-2"
    aria-selected="false"
    aria-controls="panel-2"
    tabindex="-1"
  >
    Reviews
  </button>
</div>

<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">
  Product description content...
</div>

<div role="tabpanel" id="panel-2" aria-labelledby="tab-2" hidden>
  Reviews content...
</div>

// Tab keyboard navigation
tablist.addEventListener("keydown", (e) => {
  const tabs = [...tablist.querySelectorAll('[role="tab"]')];
  const index = tabs.indexOf(document.activeElement);

  let newIndex;
  switch (e.key) {
    case "ArrowRight":
      newIndex = (index + 1) % tabs.length;
      break;
    case "ArrowLeft":
      newIndex = (index - 1 + tabs.length) % tabs.length;
      break;
    case "Home":
      newIndex = 0;
      break;
    case "End":
      newIndex = tabs.length - 1;
      break;
    default:
      return;
  }

  tabs[newIndex].focus();
  activateTab(tabs[newIndex]);
  e.preventDefault();
});

Debugging Tips

// Log what screen reader sees
function logAccessibleName(element) {
  const computed = window.getComputedStyle(element);
  console.log({
    role: element.getAttribute("role") || element.tagName,
    name:
      element.getAttribute("aria-label") ||
      element.getAttribute("aria-labelledby") ||
      element.textContent,
    state: {
      expanded: element.getAttribute("aria-expanded"),
      selected: element.getAttribute("aria-selected"),
      checked: element.getAttribute("aria-checked"),
      disabled: element.disabled,
    },
    visible: computed.display !== "none" && computed.visibility !== "hidden",
  });
}

Best Practices

Do's

• Test with actual screen readers - Not just simulators
• Use semantic HTML first - ARIA is supplemental
• Test in browse and focus modes - Different experiences
• Verify focus management - Especially for SPAs
• Test keyboard only first - Foundation for SR testing

Don'ts

• Don't assume one SR is enough - Test multiple
• Don't ignore mobile - Growing user base
• Don't test only happy path - Test error states
• Don't skip dynamic content - Most common issues
• Don't rely on visual testing - Different experience