I just saw a "rotor malfunction" in tests, and thought - what if mechanism breaks, and cant move to the right - this means we cant choose all the letters to the right of where it stopped, they are determined by previous moves of all the rotors and the initial state of the line. Does this make sense?

I don't know what you mean. Lines and rotors are input. Input is guaranteed to be sane.

Very interesting kata, thanks! A quick suggestion though - my first solution would not work have worked, if a line would have a greater length than rotor rotations array. And tests didnt count on that, so it worked anyways. Shouldnt those cases be included?

What an awful description. It simply doesnt tell the case swapping rules in the top part. Also you could shorten the description by half at least.
You could narrow it down to: "Each character case in string A should be changed N times, where N is the number of times the same character occured in the string B, regardless of its case."

Fixed, thanks.

there's mistake in description --> "di" = 4

c00l

Great kata, awesome description, thanks! :)

Thanks

the only guy having fun here :) tried similar stuff, but gave up...

fixed + upgraded to JUnit 5

great kata, thanks! learned something new :)

great kata, worst description ever though

little hard, but very very good kata, thanks!

description probably should specify there will be only integer numbers in test cases