Either copy your code and hit Reset button at the bottom, or simply click Attempt. I don't see how it wouldn't work, I ran it myself and it passed.

But your current code passes all tests. Did you modify sample tests for this error to happen?

The error message indicates that the function name used in the test cases is evenOrOdd, but your function is named even_or_odd. JavaScript is case-sensitive, so the function name must match exactly what is expected by the test cases.