Understanding Test Rules for WCAG Success Criteria

Test Rules provide guidance for developers of automated testing tools and manual testing methodologies, to help ensure consistent interpretation of WCAG Success Criteria.

W3C's List of Test Rules for WCAG 2 is updated periodically. They are developed according to the Accessibility Conformance Testing (ACT) Rules Format 1.0 standard.

Understanding Conformance provides related information, including on understanding accessibility support.

Test Rules Rules are Informative

Test Rules are informative — that means they are not required for determining conformance. The basis for determining conformance to WCAG is the success criteria from the WCAG standard — not the Test Rules.

While W3C's List of Test Rules for WCAG 2 are reviewed by the W3C Accessibility Guidelines Working Group (AGWG), they are not vetted to the same degree as the W3C Web Content Accessibility Guidelines (WCAG) standard (called W3C Recommendation). The WCAG standard is the normative reference on determining conformance.

Test Rules are Partial Checks

Test Rules typically check specific aspects of WCAG success criteria. For example, that a table cell has a header rather than the entire WCAG 2.2 success criterion 1.3.1 "Info and Relationships", which applies to many more information structures on a web page. In fact, this example rule would not even check the validity of the table header, only if the header exists for a given table cell.

Test Rules are also technology-specific. For example, the aforementioned table header example would be specific to HTML, possibly enriched with WAI-ARIA roles and properties, but not to other formats with tables. WCAG 2.2 success criteria are designed to be technology-agnostic and applicable to all web technologies.

Test Rules Check for Failures

Test Rules are designed to check failures in satisfying WCAG success criteria. That is, when content fails Test Rules, it means that the content does not satisfy the corresponding success criteria. However, when content passes Test Rules, it means that no corresponding failures were detected — it does not necessarily mean that the content satisfies all aspects of the corresponding success criteria.

The reason for this is because WCAG success criteria typically cover several aspects and technologies, while Test Rules only check specific aspects. Checking that content satisfies all aspects of WCAG success criteria typically requires further verification by human testers.

Note

WCAG 2 Conformance Requirement 1 allows for "conforming alternate versions". That means that content may still conform to WCAG 2, even when content fails Test Rules, thus does not satisfy the corresponding success criteria.

Structure of Test Rules

Test Rules conform to the Accessibility Conformance Testing (ACT) Rules Format 1.0 standard. They include the following parts: