No language specified and no code example provided. This kata has been solved a great amount of times, it's very likely your code doesn't work correctly. Please read carefully this before raising an issue: https://docs.codewars.com/training/troubleshooting/

JUnit uses square brackets to show which part of the actual/expected strings is different; not an issue.

There's no issue. The error message is correct.

'!c(TTHQTTFu'
'((())(())(('
    TT  TT

The T's are duplicates. All others are unique.

You are wrong
What about "http://vk.com"??

if my solution was accepted, then the tests are not written correctly?

Test for: s1="tMsRvWCNYh"  s2="TMSRvWCNyh"
Expected: 'false', instead got: 'true'

What's wrong with this?
The letter M at index has same case in both of the string, hence the result should be false.

Can you please tell me the programming language and the problem with them?

Please double check your random tests. Thank you.

Hey guys,
what do you think about that method?