Difference between revisions of "Accessibility Testing"

Revision as of 02:54, 6 February 2009

Accessibility is not the same as usability, but it overlaps because a lot of disabilities make it harder to deal with stuff which doesn't have great usability to begin with.

Some accessibility features can be tested automatically with tools - eg markup validation, colour contrast analysis - but much of it comes down to human judgement.

Good description here of what can and can't be tested: What accessibility testing is possible Even that site misses some stuff - contrast levels appropriate for dyslexics, moving image problems that people with some neuro deficits have, everything important being keyboard-only accessible, and probably other things.

General

These things are generally good things to do and also have implications for disability accessibility.

• Pages need to validate fully to whatever DTD they've specified.
• Pages should degrade gracefully in the absence of capabilities for Flash, JavaScript, images, CSS, etc.
• Proper semantic markup should be used, eg headers for headings, ACRONYM and ABBR tags, EM/STRONG rather than I/B tags.
  • This especially. The site should rewrite I/B tags, made in posts, into EM/STRONG, instead of the other way around which is what the current LJ code does. And the headers, oh my god, the headers. branchandroot

Blindness

This is the disability people usually think about when they discuss web accessibility, but it's important to remember it's not the only one.

• CAPTCHAs need audio options.
• Screen reader friendliness. Try very hard to get general screen reader users to do testing for us, rather than sighted people using screen readers which is a bad approximation.
  • JAWS
  • WindowEyes
  • VoiceOver
  • NVDA
  • Orca?
  • others?
• Check tab order for everything, especially things which are AJAXey and therefore have changing tab order

Relevant reading:

• WebAIM screen reader survey results

Color Blindness

• Things which are usually signalled to users through colour changes in interface elements must have some other signalling mechanism (such as change of image shape) in addition

Deafness

• Any official videos put on the site (eg "how to use" screencasts) should have captions available.

Deafblindness

This disability is a double-whammy as many of the solutions to problems faced by blind or deaf users rely on the other sense - eg audio alternatives to CAPTCHAs.

• CAPTCHAs are completely inaccessible and an alternative such as emailing support needs to be available whenever CAPTCHAs are used. Currently I think this is only journal creation, if that.
• Even captions for videos will probably be inaccessible. Separate methods of obtaining the information such as transcripts are needed.
• Information needs to be concise. Many deafblind users will be using braille displays which give a single line of text that's 40 characters long.

Dyslexia

• Contrast (too high can be a problem)
• CAPTCHAs can be inaccessible, even with audio alternatives, due to visual and auditory "noise"

Keyboard-only Users

• Make sure anything triggered usually by mouse movements (eg :hover attributes) which is needed for site use has a keyboard-accessible alternative.
• Check tab order for everything, especially things which are AJAXey
• Potentially hideable alternative text for all images which are used for site navigation and control (e.g. the "tag/memory/etc." icons) for direct keyboard access. Note this is not the same as alt tags.

Low Vision

• Contrast (low is a problem)
• CAPTCHAs need audio equivalents
• Default font size should be reasonable
• Robustness of layout to font size increases (eg command-+/ctrl-+) must be tested.
  • IE
  • Firefox
  • Safari
  • Opera
  • Others?
• For those browsers that have the capability, page size increases - scaling images as well as text - must also be tested.
  • Firefox3
  • Beta versions of Safari?
  • Others?
• Alternate layouts with less visual "clutter"/"noise" may be needed for some people (equivalent to LJ's Lynx site scheme)

Mouse use problems

Users who are able to use a mouse but have some difficulty with it. Keyboard equivalents are a solution to some in this group, but some in this group will have no ability to use a physical keyboard either - only an on-screen keyboard (again, requiring mousing) will be used.

• Mouse targets need to be as large as possible.
• Minimise/eliminate use of any elements which require a mouse click-and-drag as this is most difficult for many users.
• Remember Fitt's law.

Neurological Problems

This category would include people on the autism spectrum, people with traumatic brain injuries, stroke survivors, and several other groups.

• Anything on the page that moves (Flash, animated GIFs, etc.) can be sufficiently distracting to make the page unreadable.
• CAPTCHAs can be inaccessible, even with audio alternatives, due to visual and auditory "noise"

Resources

• Color Contrast Analyser checks for contrast which is too high as well as contrast that is too low.