screen-reader-testing – Coding skill for AI agents

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

| Screen Reader | Platform | Browser | Usage |

| ------------- | --------- | -------------- | ----- |

| VoiceOver | macOS/iOS | Safari | ~15% |

| NVDA | Windows | Firefox/Chrome | ~31% |

| JAWS | Windows | Chrome/IE | ~40% |

| TalkBack | Android | Chrome | ~10% |

| Narrator | Windows | Edge | ~4% |

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

| Mode | Purpose | When Used |

| ------------------ | ---------------------- | ----------------- |

| Browse/Virtual | Read content | Default reading |

| Focus/Forms | Interact with controls | Filling forms |

| Application | Custom widgets | ARIA applications |

Before testing on macOS, read [VoiceOver setup, commands, and checklists](references/voiceover.md).

For the required iOS Safari coverage, read [VoiceOver touch setup and gestures](references/voiceover-ios.md).

Before testing with NVDA, read [NVDA setup, modes, commands, and test scripts](references/nvda.md).

Before testing with JAWS or TalkBack, read [platform setup and commands](references/jaws-talkback.md).

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