First of all, thank you very much for your detailed answer!

I think you are right about your three points.
[1] The parameter/variable names are changed to hyphen conventional symbol names.
[2] I have refactored the example test to be (hopefully) much clearer.
[3] Invalid input values are now ignored.

By the way: I also took this opportunity to add a random test.

Good point. I changed it.

Also a good hint. I add messages to the test cases.

Yes, that is a good point. When the swimmer dose not move, he can not swim any distance.
I adapt the kata.