This is a great kata, I just think that the description is slightly misleading as it should mention that the test cases will include not just spaces, but other special characters too.
Also, the sample test cases don't include any examples with other special characters, so I didn't realise that I needed to adapt my code for special characters until I attempted the challenge & saw the random test cases.

Just noticed a small typo that should be corrected, "exemple" should be example

One of the sample tests are written incorrectly: test.assert_equals(index([5, 6], 0), 1). In the description, it says the output should be -1 if index N is not in the array, but the sample test expects an output of 1.

There is only one sample test in Python. I believe a few more tests should be added.

This is a really fun kata! I just think that the instructions could be a bit more clearer. Maybe include one or two examples in the Description?