The test is this:

testing(["it","wkppv","ixoyx", "3452", "zzzzzzzzzzzz"], 3, "ixoyx3452zzzzzzzzzzzz")

Somehow you're printing the input after sorting it from largest to shortest it seems.

Test Case is ["zzzzzzzzzzzz", "wkppv", "ixoyx", "3452", "it"], 3

It's not the test case. There are no errors in the tests.
Before posting issues look at the top of the page: 492 people passed the Swift kata. If there were errors somebody would already seen them before you:-)

Aha nice one - good luck on your Swift journey!

Hi and welcome to Codewars!

For future reference, please state which language you are working in - here, Swift it seems - so someone who knows that language can help you (I'm a Python noob so I can't look at the Swift tests).

In the mean time, please read this page on Troubleshooting - especially the part on printing the input which will allow you to see which test cases are causing you to fail:

https://docs.codewars.com/training/troubleshooting/#error-messages-and-printing-your-inputoutput

Maybe this will allow you to notice why your code is failing - large numbers, presence of 0, negative signs, etc??