No sample tests.

hi,

if any element is greater than 300 or less than 300.

you sure?

Other than that:

• would need random tests
• manual sort katas have already been done several time and it's a nightmare to enforce (especially in python). And since CW is TDD based, you have to enforce the user to not use builtins (don't bother, you won't win at that game). Meaning you're currently combining a duplicate and a somewhat bad idea.
• using different return types is a bad idea.

cheers

I will possibly add checking if any element is over 300 0r less than 0.

I would add the exceptions or something like this:
test.assert_equals(sort([100, 999, 97, 345]), 'Device is broken')