Web Accessibility Testing
The information here is from Chapter 13 of the new book, Web Accessibility: Web Standards and Regulatory Compliance, by Jim Thatcher, Andrew Kirkpatrick, Richard Rutter, Christian Heilmann, Cynthia Waddell, Michael R. Burks, Shawn Lawton Henry, Bruce Lawson, Mark Urban, and Patrick H. Lauke, published by Friends of Ed, July, 2006.
There are many sophisticated software tools that can be used to check for web accessibility. US federal agencies and corporations are spending millions of dollars on such tools that claim to test web sites for accessibility. We want to raise the question here of what can and cannot be tested with these tools. Then we will examine six commercial tools in some detail and compare their results on a set of forty test files.
Any accessibility testing must be viewed as a process that combines automated software tools with human judgment. No tool exists that you can run against your web site (or web page for that matter) in order to assert that it is accessible and/or complies with the Section 508 provisions or the Web Content Accessibility Guidelines, however much you are willing to pay. When a web site claims Section 508 Conformance or WCAG Conformance from some tool or other (and many do it), the most it can mean is that the site (or page) passed all of the automatic Section 508 or WCAG tests.
Having said that, software-testing tools can help you find out if your site is not accessible or does not comply with WCAG or Section 508, by testing for the absence of valid required elements and/or attributes.
Our information on software testing for web accessibility is divided into five sections including this introduction. When you are reading this material, links to the five sections are in the sidebar navigation.
In the second part we will use the Section
508 Web Accessibility Standards to discuss the extent to which you can rely
on software tools to check your web content for accessibility, compared to how much you must rely on human evaluation.
I will call these two parts of the job the “algorithmic” part and the “judgment” part. Algorithmic testing generally
verifies that a valid element or attribute is present – like the
alt attribute or the
for instance. Judgment comes in with questions such as whether or not the value of the
alt attribute conveys
the function of an active image, or the information in an inactive image.
Next we will look at six commercial software tools for testing accessibility and the process of using each tool for checking the test files. The fourth part describes the individual test files and the tool dealt with each file. Finally in summary we present a table of all the tests and all the tools with some concluding remarks.