Manual Accessibility Testing Skill

Canonical source:
examples/MANUAL_ACCESSIBILITY_TESTING_GUIDE.md
in
mgifford/ACCESSIBILITY.md
This skill is derived from that file. When in doubt, the example is authoritative.

Apply these rules when planning or reviewing manual accessibility testing.

Severity Scale (this skill)

Level	Meaning
Critical	Issue completely blocks a core task for one or more disability groups
Serious	Significantly impairs access; workaround unreasonable to expect
Moderate	Creates friction; workaround exists and is not too burdensome
Minor	Best-practice gap; marginal impact on access

Core Principle

Manual testing reveals issues that automated tools cannot detect, including:

Screen reader announcement quality and user experience
Keyboard navigation flow and logical sequence
Focus management in dynamic interfaces
Context and orientation for assistive technology users
Forced colors mode (Windows High Contrast) — automated tools cannot simulate OS-level color overrides
Real-world usability barriers

Critical: When Manual Testing Is Required

Perform manual testing:

Before each release — test critical user flows end to end
After UI changes — test all affected components
For new features — test complete user workflows
When automated tests pass — validate actual user experience
When accessibility bugs are reported — reproduce and verify fixes

Getting started: test keyboard-only first (easiest entry point), then learn basic screen reader commands for your platform. Practice on familiar websites before testing your own. Focus on one component or flow at a time.

Critical: Keyboard-Only Testing

Every interactive element must be reachable and operable by keyboard alone.

Steps:

Click in the browser address bar, then press Tab to start from page top
Tab through entire page; check each focusable element:
- Is focus visible (clear outline or highlight)?
- Is focus order logical (follows visual/reading order)?
- Can you activate it? (Enter for links/buttons, Space for buttons/checkboxes)
Press Shift+Tab to reverse through elements
Confirm there are no keyboard traps (can you Tab away from every element?)

Key shortcuts to verify:

Key	Expected behaviour
Tab	Move focus forward
Shift+Tab	Move focus backward
Enter	Activate links, buttons, submit forms
Space	Activate buttons, toggle checkboxes
Arrow keys	Navigate within components (menus, tabs, radio groups)
Escape	Close dialogs, cancel operations
Home / End	Jump to start/end of component

Component-specific checks:

Forms: all fields reachable; labels and required state announced; errors appear and are announced; Enter submits; can cancel/reset if applicable
Buttons: Enter and Space both activate; visual feedback on activation; focus moves appropriately after activation
Links: Enter activates; destination clear from link text; skip links work
Dropdowns/select menus: arrow keys navigate options; Escape closes; selected value announced
Modal dialogs: focus moves in on open; focus trapped inside; Escape closes (unless critical); focus returns to trigger on close
Custom widgets (tabs, accordions, carousels): follow WAI-ARIA keyboard patterns; arrow keys and Home/End work as documented; state changes are clear

Critical: Screen Reader Testing

Recommended platform pairings:

NVDA + Firefox or Chrome (Windows)
JAWS + Chrome or Firefox (Windows)
VoiceOver + Safari (macOS / iOS)
TalkBack + Chrome (Android)

Basic test procedure:

Start screen reader (NVDA: Ctrl+Alt+N; VoiceOver macOS: Cmd+F5)
Navigate by headings (NVDA/JAWS: H / Shift+H) — do they form a logical outline?
Navigate by landmarks (NVDA/JAWS: D / Shift+D) — are
```
<nav>
```
,
```
<main>
```
,
```
<header>
```
identified?
Navigate by form controls (NVDA/JAWS: F / Shift+F) — are labels announced?
Read all content — is order logical? Any missing or confusing announcements?

Component-specific screen reader checks:

Images: decorative images ignored (empty alt/
```
aria-hidden
```
); informative images have descriptive alt text; complex images have longer descriptions
Links: purpose clear from announcement alone; text meaningful (not "click here"); external links/new windows indicated
Buttons: label describes the action; pressed/toggle state announced; disabled state announced
Form fields: label announced before field type; required state, instructions/hints, error messages, and success messages all announced
Dynamic content: new/deleted content announced via live regions; loading states and progress communicated
Tables: navigate by rows/cells (Ctrl+Alt+Arrow in NVDA/JAWS); column and row headers announced with each cell; table purpose clear (caption or
```
aria-label
```
)
Custom widgets: role announced (e.g., "tab", "menu", "dialog"); state announced (e.g., "selected", "expanded"); instructions provided for complex widgets

For each interactive element, verify:

Element type is announced (button, link, heading…)
Label/name is clear and descriptive
Current value is announced (form fields)
State is announced (checked, selected, expanded…)
Changes are announced (dynamic updates, live regions)

Serious: Forced Colors Mode Testing

Why automated tools miss this: forced colors is triggered by an OS-level setting that replaces all author-defined colors with a constrained system palette. Automated tools cannot simulate the OS-level override, detect which elements become invisible when custom colors are stripped, or assess whether focus indicators/icons/custom controls survive the substitution.

How to enable:

Windows 11: Settings → Accessibility → Contrast themes → choose a theme → Apply
Windows 10: Settings → Ease of Access → High Contrast → turn on (or
```
Alt+Left Shift+Print Screen
```
)
Chrome/Edge DevTools: F12 → More Tools → Rendering → "Emulate CSS media feature forced-colors" →
```
active
```
Firefox:
```
about:config
```
→
```
ui.forcedColors
```
→ set to
```
1
```
(
```
-1
```
to reset)
Polypane includes a forced-colors emulation panel

Always verify with real OS settings before release — DevTools emulation is convenient but not fully equivalent.

What to look for:

All text is readable against its background (
```
CanvasText
```
on
```
Canvas
```
)
Buttons have a visible boundary; links distinguishable from body text; form fields have visible borders
Keyboard focus outlines are visible (
```
outline
```
is preserved;
```
box-shadow
```
may not be)
SVG icons are visible (use
```
currentColor
```
for
```
fill
```
/
```
stroke
```
)
Custom checkboxes / radio buttons remain visible and distinguishable; toggle state shown via text/ARIA/outline, not color alone
Error states are identifiable without relying on color alone; required fields marked with text or icons, not only color
Background images that convey meaning have a text/ARIA alternative
Charts/data visualizations use pattern/texture/label alternatives

Common fixes:

Issue	Fix
`box-shadow` focus ring disappears	Replace with `outline`
SVG icon invisible	Use `currentColor` for `fill` / `stroke`
Custom checkbox invisible	Add visible border; use `forced-color-adjust` override
Error marked by color only	Add icon, text label, or `aria-invalid`
Input invisible ( `border: none` )	Add `border: 1px solid ButtonBorder` in `@media (forced-colors: active)`
Background image removed	Add visible text, caption, or `aria-label`

CSS system color keywords for patching:

css

@media (forced-colors: active) {
  :focus-visible {
    outline: 3px solid Highlight;
    outline-offset: 2px;
  }
  .custom-checkbox::before {
    forced-color-adjust: none;
    border: 2px solid ButtonBorder;
    background-color: ButtonFace;
  }
  .custom-checkbox[aria-checked="true"]::before {
    background-color: Highlight;
  }
}

Relevant keywords:

Canvas

CanvasText

ButtonFace

ButtonText

ButtonBorder

Highlight

HighlightText

LinkText

VisitedText

GrayText

Use

forced-color-adjust: none

only as a last resort — it opts the element out of forced colors entirely and can negate the user's accessibility settings.

Moderate: Visual Accessibility Checks

Color contrast

Normal text (< 18 pt or < 14 pt bold): 4.5:1 minimum
Large text (≥ 18 pt or ≥ 14 pt bold): 3:1 minimum
UI components and graphics: 3:1 minimum
Focus indicators: 3:1 against adjacent colors

Test with: WebAIM Contrast Checker, browser DevTools. Test light and dark color modes separately.

SC 1.4.4 Resize Text vs. SC 1.4.10 Reflow — do not conflate

These are two distinct success criteria with different tests. A page can pass one and fail the other, and horizontal scrolling at 200% zoom is not automatically a failure of either.

SC 1.4.4 Resize Text (AA): content must be resizable up to 200% without loss of content or functionality. Checks text enlargement specifically — it does not itself require eliminating horizontal scrolling.

Set browser zoom to 200% (Ctrl/Cmd + +)
Verify all content is readable and not cut off or overlapping
Verify functionality (menus, forms, controls) still works at 200%
Also test with OS-level screen magnification (Windows Magnifier, macOS Zoom)

SC 1.4.10 Reflow (AA): content must be presented without loss of information or functionality, and without requiring scrolling in two dimensions, at a viewport width equivalent to 320 CSS pixels (a common way to test this on desktop is a 1280px-wide viewport at 400% zoom — the two are equivalent).

Set the viewport to 320 CSS pixels wide (or 400% zoom on a 1280px viewport)
Verify content does not require horizontal scrolling to read, for non-excepted content — see the exception below
Verify no content is cut off, overlapped, or hidden
Verify interactive elements remain operable
Verify reading order, relationships, and operation are preserved without relying on the original visual layout

The exception, precisely: SC 1.4.10 exempts only parts of content that require two-dimensional layout for their usage or meaning — not the page as a whole. Normative examples: data tables, maps, diagrams, video players, games, presentations, interfaces requiring a persistently visible toolbar. An excepted component does not exempt the rest of the page (the heading above a data table, filters, search, pagination must still reflow). Within an excepted component, individual sections may still need to reflow. "Requires" is a meaning test, not a convenience test — a component that merely looks better in a wide fixed layout, without losing information or functionality if it reflowed, is not exempt.

A page that triggers horizontal scroll at 400% zoom (or the 320px equivalent) is a high-value indicator that Reflow has not been achieved, but investigate whether the overflowing content falls within the exception before concluding a failure. See Behavioral Accessibility Automation (

skills/behavioral-a11y/SKILL.md

) for a reusable, tested Playwright Reflow risk indicator and its documented limitations — it is an indicator, not a Reflow conformance check; human judgment is still required to confirm the exception, verify content isn't cut off, and test actual content at 400% zoom.

Focus indicator: three distinct success criteria

SC 2.4.7 Focus Visible (AA): every keyboard-focusable element must have a visible focus indicator. Binary check — either a visible indicator exists or it does not.

Focus indicator is visible for every focusable element
Focus indicator is not removed unless replaced with a superior alternative
Focus indicator is not obscured by other content

SC 1.4.11 Non-text Contrast (AA): focus indicators on UI components must have a contrast ratio of at least 3:1 against adjacent colors. Applies to the indicator itself, not the component's normal state.

Focus indicator contrast meets 3:1 against adjacent colors, measured against the indicator color and the adjacent background/component color
Custom focus styles meet the contrast requirement (not just the default outline)

SC 2.4.13 Focus Appearance (AAA): stricter than SC 2.4.7 — requires a minimum area equal to the focusable element's perimeter × 2 CSS pixels, a 3:1 contrast ratio between focused and unfocused states, and the indicator must not be fully obscured by author-created content. Projects targeting AA are not required to meet this, but meeting it provides stronger accessibility; document whether your project targets it.

Behavioral screenshot-difference testing: the CWAC project's

FocusIndicatorAudit

sends real Tab presses and compares whole-page screenshots before/after each press, reporting a finding when no pixels changed. It does not measure contrast (SC 1.4.11), prove a detected change is local to the focused element (its comparison is whole-page), determine an indicator is sufficiently perceptible, or distinguish a missing indicator from one obscured by other content. This repository's own reusable implementation (

skills/behavioral-a11y/SKILL.md

focus-visible-risk.mjs

) is an independent reimplementation of the documented method that instead captures a fresh unfocused/focused screenshot pair scoped to a padded region around each element, closing some of CWAC's whole-page limitations while introducing its own documented tradeoffs. Neither implementation, nor any screenshot-diff approach alone, verifies SC 1.4.11 (contrast) or SC 2.4.13 (minimum area). Use screenshot-difference testing as a supplementary check alongside manual verification, not as a sole focus indicator test.

Testing Workflows by Component Type

Forms: navigate to form with keyboard only → fill all fields (check Tab order) → trigger validation errors → verify errors appear and are announced → correct and revalidate → submit with Enter/Space → verify success message is announced. With a screen reader, also confirm field labels/instructions/types are announced and errors are in logical reading order.

Modal dialogs: activate trigger → verify focus moves into modal → Tab through all elements → verify Tab doesn't leave modal (focus trap) → Escape or close button dismisses → verify focus returns to trigger. With a screen reader, confirm the modal is announced (

role="dialog"

aria-labelledby

) and content is in logical reading order.

Single Page Applications: click a navigation link → verify content changes → verify focus moves to main heading/content → verify page title changes → verify the route change is announced or focus provides context. Confirm the back button works and new page structure (landmarks, headings) is clear.

Documenting Test Results

For each issue found, record: component/page tested (URL or name), issue description, expected behavior, numbered steps to reproduce, assistive technology name/version, browser name/version, OS name/version, and severity. Optionally include a screenshot/recording and the WCAG success criterion violated.

markdown

## Accessibility Issue: [Brief Description]

**Component:** [URL or component name]
**Issue:** [Description of what doesn't work]
**Expected:** [What should happen]
**Severity:** [Critical/High/Medium/Low]

**Steps to Reproduce:**
1. [Step 1]
2. [Step 2]

**Testing Environment:**
- **Screen Reader:** [Name and version]
- **Browser:** [Name and version]
- **OS:** [Operating system and version]

**WCAG Criterion:** [If applicable]
**Suggested Fix:** [If you have one]

(For structured findings, use

skills/bug-reporting/SKILL.md

Encouraging Participation from People with Disabilities

People with disabilities are the experts in identifying barriers and validating solutions — their lived experience surfaces issues automated tools and non-disabled testers miss, and validates that fixes actually work.

Remove barriers to participation: clear jargon-free instructions, flexible timeframes, asynchronous feedback, compensation for testing time, accessible issue-reporting formats
Invite diverse testers: screen reader users, keyboard-only users, voice control users, users with cognitive disabilities, users with multiple disabilities
Credit and compensate testers fairly; create opportunities for ongoing involvement

Quick Reference Checklists

30-minute keyboard-only test: Tab start to end; focus visible everywhere; activate all buttons (Enter/Space) and links (Enter); fill and submit a form; open/close a modal; use custom widgets; navigate menus; check for keyboard traps.

30-minute screen reader test: navigate by headings, landmarks, and form fields; read full page content; activate buttons/links; fill and submit a form; test a custom widget; verify images have alt text; verify dynamic content updates are announced.

Visual accessibility quick check: 200% zoom; focus indicator visibility; color contrast (text and UI components); content readable without color alone; light and dark modes; forced colors mode.

Definition of Done Checklist

Keyboard-only test completed; all interactions reachable and operable
No keyboard traps found
Focus order is logical
Screen reader test completed with at least one platform combination
All images, icons, and charts have correct text alternatives
Dynamic content changes are announced by screen reader
Color contrast verified for text and UI components
Forced colors mode tested for all custom UI components
Zoom at 200% tested; no content cut off or horizontally scrolling
Component workflow tests run for forms, modals, and SPA navigation where applicable
Findings documented with URL, element, WCAG SC, severity, and steps to reproduce

Key WCAG Criteria

1.1.1 Non-text Content (A)
1.3.1 Info and Relationships (A)
1.4.1 Use of Color (A)
1.4.3 Contrast Minimum (AA)
1.4.11 Non-text Contrast (AA)
2.1.1 Keyboard (A)
2.1.2 No Keyboard Trap (A)
2.4.3 Focus Order (A)
2.4.7 Focus Visible (AA)
2.4.11 Focus Appearance (AA — WCAG 2.2)
4.1.2 Name, Role, Value (A)
4.1.3 Status Messages (AA)

References

Full guide
```
skills/behavioral-a11y/SKILL.md
```
— Reflow risk and Focus Visible risk automated indicators, and their documented limitations
WebAIM: Testing with NVDA
WebAIM: Using VoiceOver
WebAIM: Screen Reader Testing
Deque: Screen Reader Keyboard Shortcuts
WAI-ARIA Authoring Practices Guide
W3C: Easy Checks - First Review
MDN: forced-colors media feature

Standards horizon: These rules target WCAG 2.2 AA. Monitor: https://www.w3.org/TR/wcag-3.0/

manual-testing

NPX Install

Tags

SKILL.md Content