Manual testing is essential to ensure that a website meets accessibility guidelines and meets a high quality functional accessibility level. Generally the testing is carried out using a range of tools, to evaluate specific issues.
Testing with browsers
Websites should be always thoroughly tested in their natural environment, which is the browser. Standard web browsers such as Internet Explorer, Firefox and Opera are powerful tools for checking the accessibility of pages as they can be adjusted to simulate various outputs of web pages.
There is also a large amount of plugins working in combination with the most common browsers. They can be used to pinpoint specific element in a page, inspect the underlying code and to easily adjust browser settings. A few examples are:
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Web Accessibility Toolbar for Internet Explorer:
The Web Accessibility Toolbar (WAT) is a plug-in for Internet Explorer that allows you to list page elements such as headings, images or frames or to disable CSS and JavaScript. It also offers shortcuts to the W3C code validators and to the Contrast Colour Analyser. The toolbar is also available for Opera and under development for Firefox.
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Web Developer extension for Firefox:
this extension offers a toolbar similar to the the WAT, but it's specifically designed for Firefox.
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Firebug extension for Firefox:
Firebug integrates with Firefox and allows you to edit, debug, and monitor CSS, HTML, and JavaScript in any web page. Firebug makes it simple to find HTML elements buried deep in the page. Once you've found what you're looking for, Firebug gives you a wealth of information, and lets you edit the HTML live.
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Firefox Accessibility extension:
the Firefox Accessibility Extension makes it easier for people with disabilities to view and navigate web content. Developers can use the extension to check their use of structural and styling markup that support functional web accessibility. It also offers support for ARIA (Accessible Rich Internet Applications).
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Colour Contrast Analyser:
available as part of the WAT but also as stand-alone application, it is primarily a tool for checking foreground & background colour combinations to determine if they provide good colour visibility. It also contains functionality to create simulations of certain visual conditions such as colour blindness.
Determining "colour visibility" is based on the Contrast Ratio algorithm, suggested by the World Wide Web Consortium (W3C). The contrast ratio is now a W3C recommendation (December 2008), to help determine whether or not the contrast between two colours can be read by people with colour blindness or other visual impairments.
Testing with assistive technology
Testing with assistive technology (AT) is important, in order to recreate the environment in which website will be used by disabled people. There is no better way to simulate how your website will appear to someone who has a disability than to use the tools they use. Running your website through assistive technology like a screen magnifier, text-based browser or screen reader to test accessibility will give you the definitive pass or fail that you are looking for. They even show up quirks you may not even have guessed were present.
There are a great many different assitive technology products available, and new ones being developed all the time. We will focus on the most popular of each of the main types screen readers, text-based browsers and screen magnifiers.
Some of these tools are free or have free demonstration versions. From a testing point of view, they will be a great benefit if you do have access to them.
Screen Readers
Screen readers will read out the content and structure of your web page in linear order, from top to bottom and left to right. A skilled screen reader user can navigate around the structure of your site via keyboard commands.
Screen readers are very complicated pieces of software. They usually have a very high learning curve, and becoming competent with one of them can take a big investment of time.
They are useful for checking that:
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You hear exactly what you see on screen.
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Your "alt" texts are useful and not too long or short.
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Forms work properly and make sense.
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Your pages work when read in a linear way.
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Your site works without a mouse (simply place you mouse out of reach and use the keyboard).
The most widely used screen readers available for Windows operating systems are:
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JAWS for Windows:
JAWS is the most used screen reader. It provides access to Windows applications, including browsers such as Internet Explorer and Firefox. A free fully working demo version can be downloaded from Freedom Scientific. It works for 40 minutes and then you need to reboot the PC to use it again.
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GW Micro Window-Eyes:
another system integrated screen reader. A 30 minutes demo or a 60 Day Evaluation are available.
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Dolphin HAL:
screen reader with Speech and Braille support. Demo available for download.
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NVDA (NonVisual Desktop Access):
NVDA is a free and open source screen reader for the Microsoft Windows operating system. Providing feedback via synthetic speech and Braille, it enables blind or vision impaired people to access computers running Windows for no more cost than a sighted person. Major features include support for over 20 languages and the ability to run entirely from a USB drive with no installation.
Screen magnifiers
Screen magnifier software will magnify the screen way beyond the normal capability of the operating system. It is used by people who have low levels of sight to bring the content up to a level that they can read. The drawback is that because of the extreme levels of magnification only a very small amount of content can be displayed on a page at a time. This can be as little as two or three letters at a time.
They are useful for checking that:
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Your layout and design is usable for people with low vision.
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That your design does not include images of text.
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The colours and contrast work well and can be changed.
ZoomText is an example of combined screen reader/magnification software. It's available to buy, and a demo version is available for download.
Text-only browsers
A text only browser will display the content of your site in text only format. It will remove all dynamic and scripted elements, colouring, multimedia and graphics and display the "alt" text. Effectively, it displays what a screen reader will read out.
It is useful for checking that content and functionality of the site works:
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without multimedia
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without scripting
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without colour
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without graphics
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Style Sheets
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how your site looks when "linearised"
Lynx is an example of free text browser.