BF traversal 1
BF traversal 2

DF traversal

And you can search for more katas where these are used somehow.

iter is tail-recursive, that's what's important, while browse* call iter only once.

Hi. Could you please give me an example of similar Kata?

My published solution already is tail-recursive, otherwise it wouldn't pass either; I just forgot to put the annptation.

Still a duplicate.

Do you have a particular existing (Scala) Kata in mind?

OK, I had a stack overflow in my solution, I didn't realize that the tree in test 5 is that big. I'm not sure whether it's possible to get better output in case of stack overflow; the header of the crashing test isn't shown for some reason unless something is printed after it, flushing doesn't seem to help.

In sample test 2 assertions
In final test 5

Still "Exit Code: 1". There are only 4 assertions, right?

Indeed! I just wanted to make a very simple one in order to experience Kata creation

Sorry, my mistake

I've done some corrections, could you please try again ?

I've passed all the tests without failures, exceptions or timing out, but got "Exit Code: 1". I suspect that the tests are structured incorrectly in some way.