This is a puzzle.

Not an issue

Can you please start off by having a proper or at least a more precise description, without it, the kata is garbage.

so there is a new fixed test to add. ;) And the author should raise up the number of random tests: 20 isn't enough (as just demonstrated by mD4ndr3. 100 is a minimum, for proper random testing, generally.

I think the test cases cannot weed out my wrong solution...for example if I try with the list ['72', '7', '7', '78', '79', '709', '94'] my solution gives the wrong answer but managed to pass all the test cases multiple times?...anyway this kata is really similar to https://www.codewars.com/kata/largest-number-arrangement/train/python

As it seems to be a "performance" kata, you should mention how many tests and up to what limit will be tested.

100101 is a really cruel penalty charge for speeding o-o