Same issue here. Can you explain better why list shouldn't be mutated in this test when function is x=>x+1 (which obiously mutates the result)?

I found the issue. At my solution I was implementing the Fighter function, which seems to already exist somewhere. Insted of that I added my methods via prototype

In Javascript random tests are terrebly wrong. Here and example of the logs of one of these tests:

Mario health:257 damage:83
vs
Marco health:828 damage:92
starts Marco

Mario recives 92, 165 health left
Marco recives 83, 745 health left
Mario recives 92, 73 health left
Marco recives 83, 662 health left
Mario recives 92, -19 health left
Expected: 'Mario', instead got: 'Marco'

Please review this