why?

You dont need to return explicit true or false.

godd im so dumb haha. thanks a bunch for your reply, that totally skipped my head.

Not an issue. Print the input.

Okay so i ran my code and it works in the test run but im getting errors in the full-suite attempt. My understanding is that if you showed me the full test inputs i can alter the code by some first rate hard coding and fool the system?? But yeah, i would appreciate it if i could see the tests im failing on, this is turning out to be a big issue as i dont know what to debug or correct. Its totally fine if you cant make that happen, i'd settle for a pdf or.. some sort of git page for the tests. Hope this message finds you in safety :)

I found a mistake in my solution.
It was rather an elementary one. :)
Thank you a lot.

Just passed the kata version of the kata and everything seems to be OK. I think you are either misinterpreting the log in some way, or have some error in your solution keeping some state between runs.

Test case in testWithOverlaps is exactly the same as test in description, and it expects the same result. They are not different.

POINT 1: Here is an example in the task:
findNthOccurrence("TestTest", "TestTestTestTest", 3) == 8

POINT 2: Here is a result for my solution:

• testsWithOverlaps
  expected:<-1> but was:<8>

this occurs for next input data:

str = TestTestTestTest
subStr = TestTest
occurrence = 3

I can't understand why there are different results for the same task...

At the beginning the class Leetspeak is declared as an independent class instead of being an inheritor of Encoder. Just "extends" is needed.