'\0\0\1\1' are four bytes. The least significant bit of the byte is 1 for the two last bytes, so we get 0b100000001 == 257.

I'll add a negative example in the example test cases

The description says “Because of the edge-cases for tiny spirals, the size will be at least 5.”

The tests verify plenty of below-5 solutions, including 0.

Just thought I'd note that you should probably fix either the description or the tests. =)

Ah, I see. I'll remove that irregularity. =)

Kata does not specify that unicode data will be passed. Specifying in description that input is utf-8 encoded bytes, and that decryption should be performed per decoded symbol and not per byte, would be helpful. =)

Also, 12157692622039625013 as test input... Not sure if the large input is really needed. It breaks xrange, which is quite possibly insanely more appropriate in the solution.

Comment in code says "range(a, b) will be studied by the function" which is not the same as "range [a, b]" (inclusive)

A test case verifying if inclusive range was used should be added. Also, comment about range(a, b) should be fixed or removed.

Would be great if the kata author could fix python test issues, still present.

>>> string
'abc'
>>> string.upper()
'ABC'
>>> string
'abc'

string.upper() does not modify the string, and is repeated twice.

Also, CODE array already exists as CHAR_TO_MORSE, as specified in comment above code =)