i’m a big fan of never using lateinit

There are some exceptions that there is no workaround, especially in Java library conversion usage in kotlins, but mostly yes

Why is that?

because the “by” operator exists.

@Michael de Kaste is correct - when you are interacting with Java libraries there are points where you must behave like Java. I've found that JPA/Hibernate entities are much easier to write using

lateinit var

because that is how the underlying mechanics of the framework operate.

I use it in tests for reflection based runners (like Spring's) with annotations like

@MockBean

Usually I try to avoid it, but it is there if you really need it.

There are no rules when writing tests 🙂