Or maybe you should find the difference between sort and sort! (note that mutating the input is a bad thing)

The following sorting snippet works in my IRB but doesn't work in the tests that are run.

Maybe because your console automatically prints out the returned values?

I don't know what you confirmed, but it works in both MRI here.

Issue not specified.

This is a sample test. If you can't pass it, your code is 100% wrong.