Flutter Tests - How to Write a Test for a Widget Tree

When you started your working with Flutter, were you guys writing tests from the beginning? Or was it something that after you became comfortable with Flutter,. then you started to look at because you had regressions? Okay, so in the project that I'm currently with, there were tests, so I can say there weren't any. When we were writing unit and integration tests, then QA engineer joined and he is responsible for writing integration tests. And then my colleague Natalie joined and she said, okay, now let's write a widget test, but we'll be testing for widget tree. And now right now we have a really good coverage. Because there were some parts of the application