Thanks for the feedback! Test 11 has a big number.

Well,

test.expect(fib(0), 0)
test.expect(fib(6), 8)
test.expect(fib(-6), -8)
test.expect(fib(-96), -51680708854858323072)

Should be

test.assert_equals(fib(0), 0)
test.assert_equals(fib(6), 8)
test.assert_equals(fib(-6), -8)
test.assert_equals(fib(-96), -51680708854858323072)

Your code still has problems. Here's a little kumite I wrote to show you:
http://www.codewars.com/kumite/54198ac50fe60a8d2e000859

Good luck!

Did you read the hint?