Testability as observability and the Accessibility Object Model

I attended a talk today by Rob Dodson on some proposals for the Accessibility Object Model that are trying to add APIs for web developers to more easily manipulate accessibility features of their apps and pages. Rob went through quite a few examples of the benefits the proposed APIs would bring, from simple type checking to defining semantics of custom elements and user actions. Unsurprisingly, the one use case that stuck out for me was making the accessibility layer testable.