You have a problem with the following tests: LargeNumbers, OrderNotImportant, RandomNegative100Numbers, RandomPositive100Numbers. I can return absolutely any number, and it will be counted as the correct answer.

Oh my god. I feel stupid. Thanks for the explanations.

with longest consecutive repetition

a is repeated two times, aaa and aaaa the longest consecutive repetition has 4 as and that's what the kata expects you to return.

See for yourself. If the string is: "bbbaaabaaaa". How many letters are there 'a'? Personally, i counted 7 and my code says the same thing. And what is written in the tests? It says: ('a', 4). Does it mean that if there are 7 letters 'a' in the line , and it is written in the tests that there should be 4, then the author made a mistake?

Not a kata issue, there's no typo.

I saw a typo in the tests. This kata has a problem in c#.

500 other people solved it in C# so I don't think this is a kata issue.

note: not a suggestion, a question.

I program in c#. An error occurred during execution. Please changed the values in the tests. You made a typo: in the "LongestAtTheEnd" method, and i dare to assume that a typo was also made in "RandomTests".