Lichess is one of the most impressive OSS web apps out there. I've spent more than 240h playing blitz on there, and it doesn't have any bugs or hiccups from wha

Lichess is one of the most impressive OSS web apps out there. I've spent more than 240h playing blitz on there, and it doesn't have any bugs or hiccups from what I can tell. Looking at the source code, two things strike me. First, the Scala backend code is incredibly easy to read and inviting. This is a great poster child of how you can a build simple, reliable app in that language. Second, I'm surprised that the UI code (written in Typescript) is essentially untested. Given the high quality of the code, I was expecting the frontend code to be thoroughly covered by tests, maybe even written in Test Driven Development. But although Jest is included, there seems to be only one test file in `ui/` (and `yarn run test` doesn't seem to work currently). Is the app tested manually after every commit?