OP solved it, closing

The Java version was removed for some reason. Closing.

I saw the problem like this with another kata a couple days ago. https://www.codewars.com/kata/do-i-get-a-bonus It also contains a Unicode char in tests.
Perhaps it needs to complain to developers of codewars?

@jcarmona I can do anything with the test cases, it always fail with this error. As you are writing here, more than 100 people make kata and then, this error suddenly appears and I don't know why :( :(

and anyone know how can i solve this problem with the test to finish the kata? there are 100 people who make it

Same thing here. It seesm that ASCII is used on the server side for encoding and there are some non ASCII chars in your test case strings. So I guess it's either change the strings to use only ASCII or find out why it's configured in such way on the backend ...
It's the second Java Kata with such issue related to characters, that I come across for the past few days.

I am having this issue as well while using Java.

Thank you for letting me know the issue. I put my own solution here and I got the same problem as you. I don't know what is wrong, everything was ok when I published the kata. However, I don't know how to fix it. When I want to change the test cases, I get this: Final Solution is invalid. (java) The solution should pass the provided test cases ...

There seems to be something wrong with your encoding for some phrases on some test cases after trying to deliver the solution.
I even tried just returning str and still got this message for Java solution:

Error: Command failed: javac -verbose -cp /home/codewarrior -d /home/codewarrior -sourcepath /home/codewarrior -cp /usr/local/groovy/lib/junit-4.12.jar:/usr/local/groovy/lib/hamcrest-core-1.3.jar /home/codewarrior/TGG.java /home/codewarrior/TestE.java ./frameworks/java/CwRunListener.java
[parsing started RegularFileObject[/home/codewarrior/TGG.java]]
[parsing completed 36ms]
/home/codewarrior/TestE.java:10: error: unmappable character for encoding ASCII
"world that a child can think; and, possibly, do it practically; you wouldn???t constantly run\n" +

...

[parsing started RegularFileObject[/home/codewarrior/TestE.java]]
[parsing completed 14ms]
[parsing started RegularFileObject[./frameworks/java/CwRunListener.java]]
[parsing completed 3ms]
[total 130ms]
27 errors

I think some of your test cases are making assumptions that return is different from null before asserting.
Maybe you could add assertNotNull to answers before asserting something else. That woul avoid nullPointers on the test case, which makes it harder to figure out what the problem with our code is.

Is there a way to check which inputs you have on your testcases?

I'm getting a Runtime Error Occurred java.lang.NullPointerException at SumOfKTest.BasicTests2(SumOfKTest.java:95) but I don't have access to that line of code.

It's the "Basic Tests bigger numbers" test, but I've tried inputing even Integer.MAX_VALUE without my code throwing exceptions, so I'm not sure what to look for.