Given an array of integers, find the one that appears an odd number of times.

That's very clear to me. And you can look at the sample tests:

test.assert_equals(find_it([20,1,-1,2,-2,3,3,5,5,1,2,4,20,4,-1,-2,5]), 5)

5 appears 3 times, and the expected answer is 5, so, it's the integer, not the times it appears.

You need to return the value of the integer that appears an odd number of times.