No idea, sometimes it's because of logs misreading, but not in this case, and sometimes it can be because you use a global var and it keeps its value between tests, read this and see if it helps: https://github.com/codewars/codewars.com/wiki/Troubleshooting-your-solution I can only see the tests and not your code so I can't see the whole picture here.

Then why, when submitting an attempt, am I receiving for one or both of those cases of the first test:

expected:<0> but was:<-1>

Both of those tests expect -1 in Java.

        assertEquals(-1,Kata.findEvenIndex(new int[] {1,2,3,4,5,6}));
        ...
        assertEquals(-1,Kata.findEvenIndex(new int[] {-8505, -5130, 1926, -9026}));