We currently have automated tests for phpunit and behat, but we don't have specific tests that ensures things are accessible now and for the future.

This is a tool that does it:

https://github.com/damyon/scrats/

Tests are defined using javascript using mocha / expect js syntax. Interaction with the page is done with a screenreader class that gives access to the chrome accessibility via the automation API.

This issue provides a command line script for running these tests against the behat site of the current moodle installation.