Do you UI test your web application?

Testing is an integral part of building complex applications, but when building as indiehackers, we (or at least I) first right code that delivers value and makes money. Everything else is secondary.

But there's a point of time when the application becomes so complex that UI testing becomes important to ensure quality. So, what is that point to you? $5k MRR? $10k?

If you already do UI tests, how is your experience with that?