First of all, there are official Web Content Accessibility Guidelines (WCAG) and Section 508 documents which you should consider researching and accepting as guidelines to follow in your accessibility testing.
There are lots of tools for accessibility test automation ranging from commercial services like tenon.io
(even though I think the API is open and free but rate-limited) to open-source and free tools like AccessSniff
, HTML_CodeSniffer
, axe
from Deque Labs and Google's lighthouse
to name a few.
There is also this list at w3.org, but not sure how up-to-date it is:
If by any chance, you are using Protractor for test automation, AngularJS team built an "accessibility" plugin for Protractor which uses Chrome Accessibility developer tools and integrates with some of the services mentioned above.