Hey Voile, Thanks for the Doc, Code updated with Random test cases.

Thanks again!!! I have updated my description,
Let me know if there is something which needs to be changed.

If we remove 5 from -55, we are left out with '-', which can't be divisible by 3 ;-) ,so have to return -1.
Thanks for asking, I have added this in description.

Hey, Thanks for your feedback. I have updated the code.

Needs test case -55 too; there's already a submitted solution that passes on 55 but will error out on -55.

It's not really explained why -55 should return -1.

When all digits are 5 and hence removed, what happens? Is it -0 or -? But 0 is considered in the family of 3, so it should return -55 maybe? What is the actual spec here?

Random tests are a mandatory component of all katas. You should start from here:

https://github.com/codingforeveryone/READMEs/blob/master/codewars/random-test-cases-for-complete-beginners.md

Null can't be family of 3.

Don't worry input will not be null.

???

Also, please organize your description, hone it out and format it properly so it's actually readable and don't look like a pile of incomprehensible patchwork.

Thanks for mentioning. Yes, 0 is divisible by 3 so it is in family of 3.
I have added a note.

Random tests needed.

0 is divisible by 3 too, so the expected behavior should be clarified.

+1