“We began by investigating aXe CLI, but soon realised it wouldn’t fit our requirements. It couldn’t check pages that required a visitor to log in, so while we could test our product pages, we couldn’t test any customer account pages. Instead we moved over to Pa11y.”

I’d love to hear more about the requirements that didn’t work with axe-cli. You can script logins in tests with axe-webdriverjs, did you try using that integration? https://github.com/dequelabs/axe-webdriverjs