I know on this site we tend toward very minimal variable names

Do we tho? Why would we?

I know on this site we tend toward very minimal variable names, but ^this kind of descriptive naming is actually best practice

/1 refers to the first matching group in regexp (so literally the pattern is that the same letter should occur twice in a row)

I like your take on this solution

this is the best practice. The previous do not check for empty string neither trim.

So many people doing it like this. Pretty crazy.

Random cases added, will generate empty strings.

Duplicate.

Was not able to make more tests. Instead I changed the description of the kata.

If there is someone who can contribute to the unit tests that would be great!

better description and more test cases are required

more test cases with different input types (e.g. not a string) are required

More test cases are required e.g.

• empty string
• value that is initially not a string (e.g. array, object, number, etc.)

IMHO listing all the methods required for kata solving makes it easier than 8kyu

More test cases. Also, unless you want this to be an easy kata then the list of list should have an unknown depth, to make it more interesting.

more test cases with different values would be very useful

Please check test cases #3 and #5, they seem to be mutually exclusive. Desrciption is also misleading