I think it's not a bug rather than lack of proper documentation. (updated)
But thanks for asking! :)

The original rules of calculating quipu is what I mentioned above. (I will update the description instead of the tests)
Do you mind to change it according to that?

yes, @myjinxin2015, because of the rules mentioned above.
It has no affect to your solution, because the expected quipu soution is the same. It's just matter of interpretation in the middle of the algorithm.

It is an interesting one! I have to say that myjinxin2015's answer ins't right..
When I found out the kata I didin't thought about corner cases like this.. :)

So the correct solution would be like this:
~ -> 0 or space

between two 0-s you have to put a space but between a 0 and 1 for example you haven't.

@~@ => 11
@~~@ => 101
@~~~@ => 1001
@ ~     ~ ~     ~ @ => 1001 (!!)
1 space 0 space 0 1

I will add more test to validate this solution. :)

oh.. thanks, fixed!

Thanks for the translation!

OH.. so the reason I could't do that with your comment because you already did it? Obvious, ok :)

Try now! I think I had connection issues and didn't update my code..

You're absolutely right, I fixed this bug! :) Thanks!