But in all seriousness, I use aXe-Coconut[1], headingsMaper[2]. Then tab through the page and make sure you can get from top left to bottom right. The cursor[focus state /ouline] should be visible the whole time and you should never lose your place.
When you are done that, if you have a Mac turn on voiceover with Command+F5 and use Safari or Chrome (more aria-support). On Windows, download NVDA[3] and FireFox. Again use the keyboard to go through the page, but listen to the screen reader and make sure everything is spoken like it looks. So a button should say, "Submit Form Button" etc. Anything that doesn't say anything, ie, " button" or say something different from what you see needs work.
The general consense of the community is that automated testing only finds 30% of issues, so you've got to test manually.
[1] https://chrome.google.com/webstore/detail/axe-coconut/iobddm... [2] https://chrome.google.com/webstore/detail/headingsmap/flbjom... [3] https://www.nvaccess.org/